Endovascular implant

ABSTRACT

A plaque tack can be used for holding plaque against blood vessel walls such as in treating atherosclerotic occlusive disease. The plaque tack can be formed as a thin, annular band for holding loose plaque under a spring or other expansion force against a blood vessel wall. Focal elevating elements and/or other features, such as anchors, can be used to exert a holding force on a plaque position while minimizing the amount of material surface area in contact with the plaque or blood vessel wall and reducing the potential of friction with the endoluminal surface. This approach offers clinicians the ability to perform a minimally invasive post-angioplasty treatment and produce a stent-like result without using a stent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/170,772, filed Jun. 1, 2016, now U.S. Pat. No. 10,278,839, which is acontinuation of U.S. patent application Ser. No. 13/153,257, filed Jun.3, 2011, now U.S. Pat. No. 9,375,327. U.S. patent application Ser. No.13/153,257 is a continuation-in-part of U.S. patent application Ser. No.12/790,819, filed May 29, 2010, now U.S. Pat. No. 10,188,533. U.S.patent application Ser. No. 12/790,819 is a continuation-in-part of U.S.patent application Ser. No. 12/483,193, filed Jun. 11, 2009, now U.S.Pat. No. 8,128,677. All of the above applications are incorporated byreference herein and are to be considered a part of this specification.Any and all applications for which a foreign or domestic priority claimis identified in the Application Data Sheet as filed with the presentapplication are hereby incorporated.

BACKGROUND Field of the Invention

This invention relates to treatment of atherosclerotic occlusive diseaseby intravascular procedures for pushing and holding plaque accumulatedon the blood vessel walls out of the way for reopened blood flow.

Atherosclerotic occlusive disease is the primary cause of stroke, heartattack, limb loss, and death in the US and the industrialized world.Atherosclerotic plaque forms a hard layer along the wall of an arteryand is comprised of calcium, cholesterol, compacted thrombus andcellular debris. As the atherosclerotic disease progresses, the bloodsupply intended to pass through a specific blood vessel is diminished oreven prevented by the occlusive process. One of the most widely utilizedmethods of treating clinically significant atherosclerotic plaque isballoon angioplasty.

Balloon angioplasty is an accepted method of opening blocked or narrowedblood vessels in every vascular bed in the body. Balloon angioplasty isperformed with a balloon angioplasty catheter. The balloon angioplastycatheter consists of a cigar shaped, cylindrical balloon attached to acatheter. The balloon angioplasty catheter is placed into the arteryfrom a remote access site that is created either percutaneously orthrough open exposure of the artery. The catheter is passed along theinside of the blood vessel over a wire that guides the way of thecatheter. The portion of the catheter with the balloon attached isplaced at the location of the atherosclerotic plaque that requirestreatment. The balloon is inflated to a size that is consistent with theoriginal diameter of the artery prior to developing occlusive disease.When the balloon is inflated, the plaque is broken. Cleavage planes formwithin the plaque, permitting the plaque to expand in diameter with theexpanding balloon. Frequently, a segment of the plaque is more resistantto dilatation than the remainder of the plaque. When this occurs,greater pressure pumped into the balloon results in full dilatation ofthe balloon to its intended size. The balloon is deflated and removedand the artery segment is reexamined. The process of balloon angioplastyis one of uncontrolled plaque disruption. The lumen of the blood vesselat the site of treatment is usually somewhat larger, but not always andnot reliably.

Some of the cleavage planes created by fracture of the plaque withballoon angioplasty can form a dissection. A dissection occurs when aportion of the plaque is lifted away from the artery, is not fullyadherent to the artery and may be mobile or loose. The plaque that hasbeen disrupted by dissection protrudes into the flow stream. If theplaque lifts completely in the direction of blood flow, it may impedeflow or cause acute occlusion of the blood vessel. There is evidencethat dissection after balloon angioplasty must be treated to preventocclusion and to resolve residual stenosis. There is also evidence thatin some circumstances, it is better to place a metal retainingstructure, such as stent to hold open the artery after angioplasty andforce the dissected material back against the wall of the blood vesselto create an adequate lumen for blood flow.

The clinical management of dissection after balloon angioplasty iscurrently performed primarily with stents. As illustrated in FIG. 1, astent 3 is a tube having a diameter that is sized to the artery 7. Astent is placed into the artery at the location of a dissection to forcethe dissection flap against the inner wall of the blood vessel. Stentsare usually made of metal alloys. They have varying degrees offlexibility, visibility, and different placement techniques. Stents areplaced in every vascular bed in the body. The development of stents hassignificantly changed the approach to minimally invasive treatment ofvascular disease, making it safer and in many cases more durable. Theincidence of acute occlusion after balloon angioplasty has decreasedsignificantly with stents.

However, stents have significant disadvantages and much research anddevelopment is being done to address these issues. Stents induce repeatnarrowing of the treated blood vessel (recurrent stenosis). Recurrentstenosis is the “Achilles heel” of stenting. Depending on the locationand the size of the artery, in-growth of intimal hyperplastic tissuefrom the vessel wall in between struts or through openings in the stentmay occur and cause failure of the vascular reconstruction by narrowingor occlusion of the stent. This may occur any time after stentplacement. In many cases, the stent itself seems to incite local vesselwall reaction that causes stenosis, even in the segment of the stentthat was placed over artery segments that were not particularly narrowedor diseased during the original stent procedure. This reaction of theblood vessel to the presence of the stent is likely due to thescaffolding effect of the stent. This reaction of recurrent stenosis ortissue in growth of the blood vessel is in response to the stent. Thisactivity shows that the extensive use of metal and vessel coverage inthe artery as happens with stenting is contributing to the narrowing.The recurrent stenosis is a problem because it causes failure of thestent and there is no effective treatment. Existing treatment methodsthat have been used for this problem include; repeat angioplasty,cutting balloon angioplasty, cryoplasty, atherectomy, and even repeatstenting. None of these methods have a high degree of long-term success.

Stents may also fracture due to material stress. Stent fracture mayoccur with chronic material stress and is associated with thedevelopment of recurrent stenosis at the site of stent fracture. This isa relatively new finding and it may require specialized stent designsfor each application in each vascular bed. Structural integrity ofstents remains a current issue for their use. Arteries that areparticularly mobile, such as the lower extremity arteries and thecarotid arteries, are of particular concern. The integrity of the entirestent is tested any time the vessel bends or is compressed anywherealong the stented segment. One reason why stent fractures may occur isbecause a longer segment of the artery has been treated than isnecessary. The scaffolding effect of the stent affects the overallmechanical behavior of the artery, making the artery less flexible.Available stenting materials have limited bending cycles and are proneto failure at repeated high frequency bending sites.

Many artery segments are stented even when they do not require it,thereby exacerbating the disadvantages of stents. There are severalreasons for this. Many cases require more than one stent to be placedand often several are needed. Much of the stent length is often placedover artery segments that do not need stenting and are merely adjoiningan area of dissection or disease. Stents that are adjusted to theprecise length of the lesion are not available. When one attempts toplace multiple stents and in the segments most in need of stenting, thecost is prohibitive since installation and material is required perstent. The time it takes to do this also adds to the cost and risk ofthe procedure. The more length of artery that receives a stent that itdoes not need, the more stiffness is conferred to the artery, and themore scaffolding affect occurs. This may also help to incite thearterial reaction to the stent that causes recurrent stenosis.

SUMMARY

There exists a continuing need to develop new and improved devices toassist in the treatment of vascular disease, including atheroscleroticocclusive disease, among other conditions, and such as for the purposesoutlined above. Some embodiments of an endoluminal staple or tack devicecan include one or more of the following features: a single column celldesign, controlled angle of struts, tapered struts, struts having morethan one sinusoidal pattern amplitude, a row of anchors, anchors in themiddle of the device, flat midline markers, simultaneous deviceplacement, and a force curve with a slope of about −0.3 N/mm or less. Incertain embodiments, an endoluminal staple is provided with a forcecurve having a slope within a range of about −0.1 to about −0.3 N/mm. Inother embodiment, an endoluminal staple is provided with a force curvehaving a slope within a range of about −0.06 to about −0.1 N/mm. Inother embodiment, an endoluminal staple is provided with a force curvehaving a slope within a range of about −0.006 to about −0.06 N/mm.

Some embodiments of a catheter based endoluminal staple device, orplaque tack, can have a single column cell design.

A catheter based endoluminal staple can include proximal and distalcircumferential members. The proximal circumferential member can bedisposed at a proximal end of the endoluminal staple. The distalcircumferential member can be disposed at a distal end of theendoluminal staple. In some embodiments, the distal circumferentialmember is the distal most aspect of the endoluminal staple and theproximal circumferential member is the proximal most aspect of theendoluminal staple. The proximal and distal circumferential members canbe connected by bridge members. The bridge members can divide an outersurface of the endoluminal staple into cells bounded by the bridgemembers and a portion of each of the proximal and distal circumferentialmembers.

A catheter based endoluminal staple can include proximal and distalcircumferential members. The proximal circumferential member can bedisposed at a proximal end of the endoluminal staple, the proximalcircumferential member having a sinusoidal configuration. The distalcircumferential member can be disposed at a distal end of theendoluminal staple, the distal circumferential member having asinusoidal configuration. In some embodiments, the distalcircumferential member is the distal most aspect of the endoluminalstaple and the proximal circumferential member is the proximal mostaspect of the endoluminal staple.

In some embodiments, the endoluminal staple can include a firstplurality of distally extending apices having a first amplitude and asecond plurality of distally extending apices having a second amplitudegreater than the first amplitude. It may also, or alternatively, have afirst plurality of proximally extending apices having a first amplitudeand a second plurality of proximally extending apices having a secondamplitude greater than the first amplitude.

In some embodiments, the endoluminal staple can include a bridge memberconnecting each apex of the second plurality of apices of the proximalcircumferential member to each apex of the second plurality of apices ofthe distal circumferential member. In addition, or alternatively, at anaxially aligned position, each apex of the first plurality of apices ofthe proximal circumferential member can be unconnected to each apex ofthe first plurality of apices of the distal circumferential member at acorresponding circumferential position.

In certain embodiments, a staple is configured with a plurality ofstruts on a circumferential member and one or more angles between thestruts is controlled. In particular, the angles of the outward apexes ofthe circumferential member can be controlled. By controlling theseangles in particular, production run quality can be improved and thestaple is better able to distribute stresses evenly along thecircumferential member.

In other embodiments, an endoluminal staple is provided that includes aplurality of circumferential members, at least one of which comprises aplurality of struts. The struts can be configured with a taper alongtheir length, to control the manner in which the struts are loaded. Thetaper can be the same or different along each strut or along each typeof strut. For example, each circumferential member can be made up of apattern of repeating struts, with each type of strut having a particulartaper. In some embodiments, the struts can alternate from a wider end toa shorter end and then the next strut can have a shorter end followed bya wider end. Other configurations are also possible, increasingly widerstruts being just one additional example.

As another example, a circumferential member with a plurality of strutscan be on a distal end of an endoluminal staple. A first strut can betapered such that a proximal portion of the strut is narrower than adistal portion of the strut. A second strut is connected to the firststrut at distal ends of the first and second struts. The second strutcan have the same or a different taper. For example, the second strutcan also have a proximal portion narrower than a distal portion of thesecond strut, while also being narrower overall than the first strut. Athird strut can be connected to the second strut at proximal ends of thesecond and third struts. The third strut can have a proximal portion ofthe strut that is wider than a distal portion of the strut. A fourthstrut can be connected to the third strut at distal ends of the thirdand fourth struts. The fourth strut can have a proximal portion of thestrut that is wider than a distal portion of the strut. The fourth strutcan have the same or a different taper from the third strut. Forexample, the fourth strut can wider overall than the third strut.

In certain embodiments, an endoluminal staple has a firstcircumferential member disposed at a distal end of the endoluminalstaple, the first circumferential member comprising a repeating patternof first and second outward apices spaced apart by first and secondinward apices. The amplitude of the second outward apices can be lessthan the amplitude of the first apices. The endoluminal staple can alsohave a second circumferential member disposed at a proximal end. Thesecond circumferential member can be a mirror image of the firstcircumferential member.

In certain embodiments, an endoluminal staple has a firstcircumferential member disposed at a distal end of the endoluminalstaple and a second circumferential member disposed at a proximal end.The second circumferential member can be a mirror image of the firstcircumferential member. The first and second circumferential members canbe connected by a plurality of bridge members. In some embodiments, thebridge members can include one or more anchors configured to engage theplaque and/or the blood vessel wall.

In certain embodiments, an endoluminal staple can be configured forsimultaneous deployment wherein the entire staple is released from thedelivery catheter prior to the staple contacting the blood vessel lumenwhere it is to be placed. Simultaneous deployment is most likely inlarger vessels, for example, vessels larger than (e.g., having adiameter that is larger than) 80% of the length of the staple willgenerally permit simultaneous deployment. For one embodiment of theendoluminal staple, such vessels include superficial femoral artery,iliac, popliteal, and tibial.

In certain embodiments, an endoluminal staple is provided with featuresthat allow the staple to remain in a delivery catheter after a deliverysheath has been withdrawn releasing at least part of, or an entirecircumferential member. The circumferential member can make up almostone half of an axial length of the staple. The staple can also beconfigured for simultaneous deployment when released.

In certain embodiments, an endoluminal staple can have a force curvewith an extended area having a low slope. A force curve plots the amountof expansive force exerted, e.g., radially outwardly directed, by a selfexpanding staple or stent when moving from a compressed state to anexpanded state. In some embodiments, the low slope of the force curvecan be over a 2.5 mm outer diameter expansion range with a change inforce of less than 1 N. In some embodiments, the slope can be less than−0.3 N/mm.

A tack device can be used in a method to treat any plaque dissection inthe blood vessel after balloon angioplasty by installing the tack withan expansion force against the plaque to hold it against the bloodvessel walls. One method encompasses one wherein balloon angioplasty isfirst performed, and if there is any damage, disruption, dissection, orirregularity to the blood vessel caused by the balloon angioplastymechanism, one or more tack devices may be used to tack down thedamaged, disrupted, dissected, or irregular blood vessel surface, so asto avoid the need to install a stent and thereby maintain a “stent-free”environment.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages are described belowwith reference to drawings of preferred embodiments, which are intendedto illustrate but not to limit the present invention.

FIG. 1 illustrates the use of a stent installed after angioplasty asconventionally practiced in the prior art.

FIG. 2 illustrates the use of plaque tacks installed after anendolumenal procedure demonstrating advantages over the prior art.

FIG. 3A shows an embodiment of a plaque tack in end view, FIG. 3B showsit in side view, FIG. 3C shows the plaque tack in perspective, and FIG.3D shows a section of the plaque tack in a flat or rolled-out view.

FIG. 4 is a schematic representation of a distal portion of a deliverydevice that has been advanced to a treatment site expanded in the bloodvessel.

FIG. 4A illustrates the proximal end of one embodiment of a deliverydevice.

FIG. 4B is a plan view of the distal portion of the delivery deviceshown in FIG. 4.

FIG. 4C is a cross-sectional view of the distal portion of FIG. 4Bshowing a plurality of tack devices prepared for implantation.

FIG. 4D shows the deployment of two tack devices upon retraction of asheath.

FIGS. 5A and 5B show another embodiment of a plaque tack in a collapsedstate and in an expanded state, respectively.

FIG. 5C shows a detail view of a section of the plaque tack of FIG.5A-B.

FIG. 5D shows a variation on the embodiment of FIGS. 5A-5C having ananchor disposed on a midline of the tack.

FIG. 5E shows a variation with struts that taper from wider at a lateraledge of a tack to narrower at a mid-section of the strut and/or fromnarrow at a mid-section of a strut to wider adjacent to a mediallocation of the tack.

FIG. 6A is a chart comparing the expansion forces of a plaque tack to astent.

FIG. 6B illustrates the use of multiple plaque tacks which are spacedapart over the length of a treatment site as compared to a typicalstent.

FIG. 7A shows another embodiment of a plaque tack in a fully compressedstate. FIG. 7D shows the plaque tack in a fully expanded state and FIGS.7B and 7C show the plaque tack in states of expansion between the fullycompressed and expanded states.

FIG. 8 is a schematic view of the focal elevating element of a plaquetack in FIGS. 7A-D.

FIG. 9 is a schematic diagram illustrating the variables for computingthe elevated tack surface due to the use of focal elevating elements ina plaque tack device.

FIG. 10 illustrates use of a plaque tack with focal elevating elementsfor holding a plaque against a blood vessel wall.

FIGS. 11 and 12 illustrate a variant use of focal elevating elements ona plaque tack.

FIGS. 13 and 14 illustrate another variant of focal elevating elementson a plaque tack.

FIG. 15 illustrates the use of focal elevating elements to reshapeartery walls into a desired cross-sectional shape.

FIGS. 16-22 illustrate variations in forming and positioning focalelevating elements on the struts of a plaque tack.

FIGS. 23-29 illustrate a method of delivery of a plaque tack into ablood vessel.

FIGS. 30A-B show a focal elevating element engaging plaque.

FIGS. 31A-B show anchors engaging plaque.

DETAILED DESCRIPTION

The subject matter of this application is directed to the improvement ofa plaque tack or staple device. The plaque tack or staple device can beused for treating atherosclerotic occlusive disease. The plaque tack canbe used to hold loose plaque against a blood vessel wall. The plaquetack can include an annular member configured to apply an expansionforce to the loose plaque.

I. Overview of Endolumenal Tack Treatment

FIG. 2 shows one embodiment of a plaque tack or staple device 5 thatincludes a thin, annular band or ring of durable, flexible material. Thetack device can be inserted into a blood vessel in a compressed stateand installed in an expanded state against the blood vessel wall using acatheter delivery mechanism at one or more specific positions of looseplaque. The plaque tack 5 can be deployed after or as part of anangioplasty procedure. The plaque tack 5 is adapted to apply anexpansion force against the plaque in the blood vessel 7 to press andhold the plaque against the blood vessel walls. The tack device can beradially outwardly expandable under a spring or other expansion force.Preferably the fully expanded diameter of the tack 5 is greater than thetransverse size of the vessel to be treated. As discussed below, thetack 5 advantageously can be deployed in a surprising large range ofblood vessel sizes.

The plaque tack 5 can include a plurality of plaque anchors 9 on itsouter annular periphery. The plaque anchors 9 can be embedded into or atleast placed in physical contact with plaque by expanding up against theplaque. In certain embodiments, the plaque anchors 9 are adapted toelevate adjacent sections of the tack 5 relative to the wall of thevessel. In at least this sense, the anchors 9 may have some of theadvantages of focal elevating elements that are discussed in SECTION IIIbelow. The anchors 9 exert a holding force on the plaque whileminimizing the amount of material surface area in contact with theplaque or blood vessel wall. As another feature, the plaque tack 5 canextend over only a small area in the axial direction of the vessel wall,in order to minimize the amount of foreign structure placed in the bloodvessel. For example, each plaque tack 5 can have an axial length L thatis only a small fraction of the axial length of a typical stent.

The plaque tack devices of the present application are designed as aminimally invasive approach to tacking loose or dissectedatherosclerotic plaque to the wall of the artery, as illustrated in FIG.2. The plaque tack may be used to treat either de novo atheroscleroticlesions or the inadequate results of balloon angioplasty. The plaquetack is designed to maintain adequate lumen in a treated artery withoutthe inherent disadvantages of vascular stents. The device may also beused to administer medications, fluid, or other treatment (“eluting”)agents into the atherosclerotic plaque or the wall of the blood vesselor into the bloodstream.

One or more plaque tacks 5 can be accurately deployed in positions alongthe length of a plaque accumulation site where specific holding forcesare needed to stabilize the site and/or hold pieces of plaque out of theway of blood flow.

FIG. 2 shows that in various plaque tack treatments, a plurality ofplaque tacks 5 can be deployed to treat locations that are axiallyspaced along the vessel 7. In this way, targeted treatments can beprovided to hold loose plaque against a vessel wall withoutover-scaffolding as discussed below. The plaque tack 5 and installationprocedure may be designed in a number of ways that share a commonmethodology of utilizing the outward force of a spring-like annular bandto enable the tack to be compressed, folded, or plied to take up asmall-diameter volume so that it can be moved into position in the bloodvessel on a sheath or catheter, then released, unfolded or unplied to anexpanded state within the blood vessel.

The plaque tack device can be delivered into the blood vessel fromendovascular insertion. SECTION IV below discusses a variety of deliverymethodologies and devices that can be used to deploy plaque tacks. Thedelivery device for the different embodiments can be the same, or can bedifferent with features specifically designed to deliver the specifictack. The plaque tack and installation procedure may be designed in anumber of ways that share a common methodology of utilizing an expansionforce of the delivery mechanism (such as balloon expansion) and/or theexpansion force of a compressible annular band to enable the tack to bemoved into position in the blood vessel, then released, unfolded orunplied to an expanded state within the blood vessel.

II. Further Embodiments of Endoluminal Staples

Variations of the plaque tack 5 can have a mesh-like configuration andcan be arranged with one or more circumferential members formed withdiscrete struts, such as in open and closed cell constructions, amongother designs.

A. Plaque Tack with Metallic Mesh Construction

An embodiment of a plaque tack 10 in the form of a metallic meshconstruction is illustrated in FIGS. 3A-D, and 4. The plaque tack 10 isshown having a closed cell construction with an annular band 10 a formedof interleaved mesh, and radially outwardly extending projections 10 b.The plaque tack 10 may be laser cut or etched out of a metal tube formor made of thin metal wire which is looped and interleaved in a meshthat is welded, soldered, looped and/or linked together into the desiredmesh shape as can be seen in FIGS. 3C-D. The projections 10 b canproject out from the annular band 10 a. The projections 10 b can be onan outer surface of the tack and can contact and/or embed into the wallof a blood vessel.

The annular band of the plaque tack 10 can have a dimension in the axialdirection of the vessel walls (sometimes referred to herein as length)that is about equal to or less than its expanded diameter, in order tominimize the emplacement of foreign scaffolding structure in the bloodvessel. Expanded diameter means final diameter in an unconstrainedexpansion. One or more tacks can be applied only in positions along thelength of a plaque accumulation site where specific holding forces areneeded to stabilize the site and/or hold pieces of plaque out of the wayof blood flow.

The mesh pattern can be designed so that the plaque tack 10 can becompressed radially inward to a smaller-volume size. This can allow theplaque tack 10 to be loaded onto or within a catheter delivery device tobe inserted into the blood vessel. For example, the tack 10 can have anoverall circular shape with bends, such as inner V bends, that allow itto be folded in zig-zag fashion to a compressed smaller-volume form forloading in a delivery catheter, such as a deployment tube.

At the desired position in the blood vessel, the compressed plaque tack10 is released from the delivery catheter. The mesh combined with anannular, ring shape can allow the plaque tack 10 to spring back to itsexpanded shape. Alternatively, the tack 10 can be expanded by anotherdevice, such as by a balloon. FIG. 3C shows the plaque tack 10 at restin its fully expanded state and FIG. 3D shows a detail of a section ofthe metallic mesh.

FIGS. 4-4D show that one or more plaque tacks 10 can be positioned in apatient's vasculature at a treatment site by a delivery device 11 withan outer sheath 13 and thereafter expanded. The tack 10 can be expandedin any suitable way, such as by being configured to self-expand or to beballoon expanded. In the illustrated embodiment, a plurality ofself-expanding tacks 10 (or variants, such as tack 10′ or tack 10″) isdisposed inside the sheath 13. The delivery device 11 includes anelongate body 11A that is disposed at least partially within the sheath13. The delivery device 11 also includes a dilating structure 11B thatatraumatically displaces tissue and helps to guide the delivery device11 through the vasculature. The body 11A can be configured with a lumen11C extending therethrough for receipt and slideable advancement of aguidewire 40 therein. In the illustrated embodiment, the sheath 13 andthe dilating structure 11B meet to provide a smooth outer surface to thedelivery device 11, e.g. having the same outside diameter where theymeet. The body 11A can be configured with a plurality of annularrecesses 11D in which tacks 10, 10′, 10″ can be disposed. The annularrecesses 11D can be defined between one or more shoulders 11E thatprevent proximal or distal slippage of the tacks along the elongate body11A. The recesses 11D could be eliminated by providing another structurefor axially fixing the tacks 10, 10′, 10″ along the elongate body 10A.

FIGS. 4A and 4D show a proximal end of the device 11 and a manner ofdeploying the tacks 10, 10′, 10″. In particular, the proximal end of thedevice 11 includes a handle 11F and an actuator 11G. The actuator 11G iscoupled with a proximal end of the sheath 13 such that proximal anddistal movement of the actuator 11G cause proximal and distal movementof the sheath 13. FIG. 4A illustrates a distal positioning of theactuator 11G which corresponds to a forward position of the sheath 13relative to the elongate body 11A and the recesses 11D. In this positionthe recesses 11D and the tacks 10, 10′, 10″ are covered by the sheath.Movement of the actuator 11G proximally relative to the handle 11Fcauses the sheath 13 to move proximally, e.g., to the position of FIG.4D. In this position, the distal most two tacks 10, 10′, 10″ areuncovered and are permitted to self-expand in the manner discussedherein.

Returning now to FIGS. 3A-B, the projections 10 b on the surface of thetack 10 can act as anchors or elevating elements to embed into or pressagainst the plaque. An array of anchors or elevating elements can beused for linking the annular band of the tack with the plaque mass orblood vessel wall. The projections 10 b can be made of a sufficientlyrigid material to sustain a locking or engaging relationship with theblood vessel tissue and/or to pierce or engage the plaque and maintainthe locking or engaging relationship therewith. The projections 10 b mayproject at an angle of 90 degrees to the tangent of the annular band, oran acute angle may also be used.

The plaque tack may be made of a material such as a corrosion-resistantmetal, polymer, composite or other durable, flexible material. Apreferred material is a metal having “shape memory” (such as Nitinol).In some embodiments, a tack may have an axial length of about 0.1 to 6mm, an expanded diameter of about 1 to 10 mm, and an anchor height from0.01 to 5 mm. In general, the annular band of the plaque tack has alength in the axial direction of the vessel walls that is about equal toor less than its diameter, in order to minimize the amount of foreignstructure to be emplaced in the blood vessel. The annular band can havea ratio of axial length to diameter as low as 1/100.

B. Plaque Tack with Open Cell Construction

FIGS. 5A-5C illustrate that in certain embodiments, a plaque tack 10′can be configured with an open cell structure. The plaque tack 10′ caninclude one or more circumferential members that have undulating, e.g.sinusoidal, configurations and that are spaced apart in the axialdirection. The circumferential members can be coupled together at one ormore circumferentially spaced locations by axially extending members,sometimes referred to herein as bridge members. These embodiments areexpandable over a wide range of diameters and, as discussed below, canbe deployed in a variety of different vessels.

The plaque tack 10′ can have features similar to those described abovewith respect to the plaque tack 10. For example, the plaque tack 10′ mayalso be laser cut or etched out of a metal tube form. Similarly, theplaque tack 10′ may be made of a material such as a corrosion-resistantmetal (e.g., certain coated or uncoated stainless steel orcobalt-chromium alloys), polymer, composite or other durable, flexiblematerial. A preferred material is a metal having “shape memory” (such asNitinol).

FIGS. 5A-B show the overall structure of the plaque tack 10′ with anopen cell arrangement. The plaque tack 10′ is shown having twocircumferential members 12, which can be rings formed by a plurality ofzig-zag struts, joined by bridges 14 that extend between the rings 12.The rings and bridges define a column of bounded cells 16 along an outersurface of the tack. The outer surface extends about an outer periphery,e.g., an outer circumference of the tack 10′. The boundary of each ofthe cells 16 is made up of a number of members or struts. As shown, thesecond ring is a mirror image of the first ring, though the first andsecond rings may be circumferential members with differentconfigurations. Also, the bridges 14 can be symmetrical across atransverse plane extending through the axial mid-point thereof, thoughother configurations are also possible. The rings 12 can be consideredcoaxial, where that term is defined broadly to include two spaced apartrings, or structures, having centers of rotation or mass that aredisposed along a common axis, e.g., the central longitudinal axis of thetack 10′.

FIG. 5C is a schematic flat depiction of a portion of a tack 10′illustrating a portion of the cell 16 and a portion of a boundarythereof. The portion illustrated to the right of the midline C is onehalf of the cell 16 in one embodiment. The other half can be a mirrorimage, as shown in FIGS. 5A-B, an inverted mirror image, or some otherconfiguration. The portion of the ring 12 that is part of an individualcell 16 can define a portion that is repeated in a pattern along thering. In some embodiments, the ring 12 can have portions that arerepeated in a pattern that extends across cells, such as across 1.5cells, 2 cells, 3, cells, etc. The pattern of the rings 12 combined withother features of the tack 10′ can enable it to be circumferentiallycompressible. The difference between the compressed and expanded statescan be seen by comparing the compressed view shown in FIG. 5A and theexpanded view shown in FIG. 5B.

The cells 16 of the tack 10′ can be bounded by portions of two rings 12,which can be mirror images of each other. Thus, some embodiments can befully described by reference to only one side of the tack 10′ and of thecell 16. The ring 12, a portion of which is illustrated in FIG. 5C, hasan undulating sinusoidal pattern. The undulating pattern can have one ormore amplitudes, such as the dual amplitude configuration shown.

The rings 12 can have a plurality of struts or structural members 26,27, 28, 29. The plurality of struts can repeat about the circumferenceof the ring 12. The struts can be many different shapes and sizes. Thestruts can extend in various different configurations. In someembodiments, the plurality of struts 26, 27, 28, 29 extend betweeninward 18, 19 and outward apices 24, 25.

In some embodiments, the outward apices 24, 25 extend axially differentdistances as measured from a central zone or midline C of the tack 10′.In particular, the apex 24 can be considered a high apex and the apex 25can be considered a low apex in this regard. The inward apices 18, 19may be axially aligned, e.g., being positioned at the same axialdistance from the midline C. Thus, the outward apex 24 is disposedfarther away from the bridge and inward apices than the outward apex 25.In some embodiments, the axial length of the tack 10′ is measured fromthe top of the outward apex 24 on one side of the cell 16 to thecorresponding top of the outward apex 24 on the other side of the cell.Put another way, the first outward apex 24 extends a first axialdistance from the midline C of the tack 10′ and the second outward apex25 extends a second axial distance from the central zone C of the tack10′, the first distance being greater than the second distance. Eachside of the cell 16 as shown has one high outward apex 24 and one lowoutward apex 25.

The bridge 14 can be connected to the one or more of the inward apices18, 19. The bridge 14 can join the two rings 12 together. The bridge 14can have many different shapes and configurations. Some embodiments ofthe tack 10′ have a proximal ring and a distal ring with the bridgedisposed between and connecting them. As mentioned above, the bridge 14can be located at the central zone or midline C of the tack 10′. In FIG.5C, the word “proximal” refers to a location on the tack 10′ that wouldbe closest to vascular access site than the portion labeled “distal”.However, the tack 10′ can also be thought of as having a medial portionthat corresponds to the midline C and lateral portions extending in bothdirections therefrom. As such, the location labeled “proximal” is also amedial location and the location labeled “distal” is also a lateralposition. All of these terms may be used herein.

As shown, the bridge 14 is connected to each ring at the inward apex 18.In some embodiments, a bridge is connected to every inward apex, forminga closed cell construction. In other embodiments, the bridge 14 isconnected to every other inward apex, every third inward apex, or spacedfarther apart by as needed, forming a variety of open cellconfigurations. The number of bridges 14 can be chosen depending uponthe application. For example, six or fewer bridges 14 may be usedbetween the two rings 12 when desired for limiting neointimalhyperplasia.

One technique for enhancing the plaque holding capability of the bridges14 is to align plaque holding structures (such as the barb 9,projections 10 b, or the anchors discussed below) with a forceapplication location or direction of the ring 12. In some embodiments,at least a portion of the bridge 14 can be aligned, with one of thestruts of the ring 12. For example, where the bridge 14 connects to thering 12, whether at an inward apex or at a strut, that connectingportion of the bridge can extend therefrom in a manner that is aligned,partially or substantially aligned with a strut. FIG. 5C shows that thebridge 14 is connected to the inward apex 18 and that the connectingportion of the bridge is substantially aligned with the strut 26. In onetechnique, a plaque holding structure of the bridge 14 is disposed on aprojection of a longitudinal axis L_(A) of the strut 26. As discussedbelow, the tack 10′ has a plurality of anchors 20. The axis L_(A)intersects a portion of an anchor 20 to maximize a torque effect fromthe expanded strut 26 to the anchor 20. In the arrangement of FIG. 5C,an anchor on an opposite side of the centerline C is disposed on theprojection of the axis L_(A) and the projection of a longitudinal axisL_(A) of a mirror image strut 26 intersects the anchor 20 of the struton the same side of the centerline C as the strut 26 shown in FIG. 5C.In another technique, the projection of the strut 26 and its mirrorimage strut can be aligned with the centerline C, which is rigidlycoupled with the anchors 20. The bridge 14 also is aligned with a highamplitude sinusoidal section of the tack 10′.

A series of unique design features can be integrated into the tack 10′for various purposes as will be discussed in more detail in the sectionsbelow. For example, the tack 10′ can include one or more of anchors,markers and focal elevating elements, among other features. As discussedabove, FIG. 5C shows that the plaque tack 10′ can include a plurality of(e.g., two) anchors 20. The tack 10′ also can include a position marker22 on each bridge 14. The position markers 22 can be fluoroscopicallyopaque and in one arrangement are generally flat. As used in thiscontext, flat markers are arranged to have a planar outer face that istangential to a cylinder that extends through an outer surface of thetack 10′ or that is concentric with the outer surface but disposedradially inside the outer surface. The anchors 20 can similarly beconfigured to be tangential to a cylinder that extends through an outersurface of the tack 10′.

As another example, a series of unique design features can be integratedinto the tack 10′ for dynamic distribution of stresses within the tack10′. These design features can enable the uniform control of the tack10′ during compression, expansion, delivery, and catheter release. Thedesign features can also individually and/or collectively manage thestresses throughout the bulk of the tack, along the struts, and at theinterface of the tack and the blood vessel lumen. Better control of thedistribution of stresses within the tack has the benefit of reducingcellular response and tack fracture by limiting strut fatigue and theassociated micro-rubbing at the tack-blood vessel interface.Micro-rubbing includes a variety of small scale adverse interactionsbetween implants and patient tissue, such as abrasion or friction thatoccurs on a cellular or intercellular level between the tack and theblood vessel lumen.

A reduction in cellular response is believed to be achieved partlythrough a reduction of surface area contact between the tack and theblood vessel lumen and partly by maximizing alignment of the contactpoints or structures with the blood vessel cells' natural orientation.Thus, the tack is able to move with the blood vessel while decreasingthe micro-rubbing. Other devices, such as stents, contact the bloodvessel cells in ways that may extend across, e.g., transversely to,multiple cells increasing micro rubbing at the stent-blood vesselinterface.

1. Single Column Cell Design

One characteristic of the embodiment the tack 10′ of FIGS. 5A-C is thatit includes a single column open cell design contained between twozig-zag rings. This arrangement provides minimal (if any) scaffolding ofa vessel. In one sense, a ratio of the vessel contact area to the totaltreatment zone of the plaque tack 10′ is small. In this context, vesselcontact area is the sum of the area of outer portions of the tack 10′that may come into contact with the vessel wall. More particularly, thevessel contact area may be calculated as a summation for all of thestruts of the length of each strut times the average transversedimension (width) of the radially outer surface of each strut. If thestruts of the zig-zag rings are laser cut, the width of the radiallyouter surface of the strut may be less than that of the radially innersurface. The vessel contact area may also include the radially outersurface of the bridges 14. The total treatment zone of the plaque tack10′ can be defined with respect to the fully expanded configuration in abest fit cylinder. A best fit cylinder is one that has an innercircumference that equal to the unconstrained circumference of theplaque tack 10′. The total treatment zone has an area that is definedbetween the proximal and distal ends (or the lateral edges) of theplaque tack 10′. The total treatment zone can be calculated as thelength between the proximal and distal ends (or lateral edges) in thebest fit cylinder times the inner circumference of the best fitcylinder. In the illustrated embodiment, the length for purposes ofdetermining the total footprint can be the distance at the samecircumferential position between high outward apices of the rings 12.

In various embodiments, the ratio of the vessel contact area to totaltreatment zone is less than 50%. In some embodiments, the ratio of thevessel contact area to total treatment zone is even less, e.g., 40% orless. The ratio of the vessel contact area to total treatment zone canbe as small as 20% or less. In specific examples, the ratio of thevessel contact area to total treatment zone is 5% or even 2% or less. Asdiscussed below, focal elevating elements can augment this advantageousfeature, even further lowering the ratio of the vessel contact area tototal treatment zone by providing separation between the vessel wall andat least a portion the circumferential members 12.

In certain methods, a vessel can be treated by implanting a plurality ofstructures, e.g., plaque tack 10′. The structures have a total contactarea with the vessel wall. The total contact area may be the sum of thevessel contact area of the individual structures. In the method, a totaltreatment zone area can be defined as the surface area between theproximal end of the most proximal structure and the distal end of thedistal most structure. In one method, the total contact area is no morethan about 55% of the total treatment zone area. More typically, thetotal contact area is between about 10% and about 30% of the totaltreatment zone area. In specific examples, the total contact area is nomore than 5-10% of the total treatment zone area.

The tack 10′ can also be understood to provide a relatively high openarea within its lateral edges compared to stents. Distinct fromtraditional stents, the track 10′ need not include sufficient metal toprovide a scaffolding function, to hold a vessel open. To accomplishmany of the contemplated treatments, the tack 10′ can be configured tolimit its contact to only a single point or a plurality of discretepoints, for example at one or more axial locations. The discrete pointscan be widely spaced apart, such as by being points on a circumferencethat are separated by spaces or, when applied, vascular tissue.

In some embodiments, the open area bounded by lateral edges of the tack10′ dominates the total footprint, as defined above. The open area ofthe tack 10′ can be defined as the sum of the areas of the cells 16 whenthe tack 10′ is in the fully expanded configuration, as defined above.The open area should be calculated at the outer circumference of thetack 10′, for example the area extending between the internal lateraledges of each of the struts. In this context, internal lateral edges arethose that form at least a part of the boundary of the cells 16. Invarious embodiments, the sum of the radially outwardly facing surface ofthe struts of the tack 10′ can be no more than about 25% of the openarea of the tack 10′. More typically, the sum of the radially outwardlyfacing surface of the struts of the tack 10′ is between about 10% toabout 20% of the open area of the tack 10′. In other examples, the sumof the radially outwardly facing surface of the struts of the tack 10′is less than about 2% of the open area of the tack 10′.

A single column design includes arrangements in a plurality of tackcells are oriented circumferentially about a central axis of the tack10′. Tack cells can come in many configurations, but generally includespaces enclosed by struts and are disposed in the wall surface of thetack. Open cell designs include arrangements in which at least some of aplurality of internally disposed struts of proximal and distalcircumferential members are not connected by bridges or axialconnectors. FIG. 5C shows that the inward apex 19 is unconnected to acorresponding inward apex on a mirror image ring 12. Thus, a portion ofthe cell 16 disposed above the inward apex 19 in FIG. 5C is open toanother portion of the cell 16 disposed below the inward apex 19. Opencell designs have increased flexibility and expandability compared toclosed cell designs, in which each internally disposed struts of aproximal circumferential member is connected to a correspondinginternally disposed struts of an adjacent circumferential member. Thecell 16 would be divided into two closed cells by connecting the inwardapex 19 to a corresponding inward apex on the mirror image ring 12. Asdiscussed above, closed cell plaque tacks can be suitable for certainindications and can include other features described herein. As shown,the single column open cell design extends along the midline C of thebridge (and also, in this embodiment, along the circumference of thetack 10′).

In one embodiment the cell 16 is identical to a plurality of additionalcells 16 that would be disposed circumferentially about the central axisof the tack 10′. The number of cells can vary depending on factors suchas the size of the vessel(s) for which the tack 10′ is configured, thepreferred arrangements of the rings 12, the number of bridges 14 to beprovided and other factors.

As discussed above, the tack 10′ can include proximal and distal rings12 connected by bridges 14. The proximal ring 12 can be disposed at aproximal end of the tack 10′. The distal ring can be disposed at adistal end of the tack 10′. In some embodiments, the distal ring is thedistal most aspect of the tack 10′ and the proximal circumferentialmember is the proximal most aspect of the tack 10′. The bridges 14 candivide an outer surface of the tack 10′ into cells 16 bounded by thebridges 14 and a portion of each of the proximal and distal rings 12. Inthe embodiment of FIGS. 5A-5C, the single column design is provided byproviding bridges at only one axial position and only a pair ofcircumferential members or rings 12. FIG. 5C includes the terms “distal”and “proximal” for reference purposes related to this and otherexamples, thus the ring 12 shown is the distal ring. In otherembodiments, the ring 12 shown can be the proximal ring.

As discussed above, the cells 16 can have one of many different shapesand configurations. FIG. 5B shows that, the cells 16 are aligned as arepeating pattern forming a single column open cell design along thecircumference of the tack 10′.

Conventional stent designs are generally relatively long (e.g., 4 cm andeven up to 20 cm when used in peripheral vasculature) from their distalto proximal ends. Where arranged with circumferentially disposed cells,conventional stents have a large number of columns of cells. Thesedesigns are burdened with repeating points of weakness and can generatestresses that become difficult to manage. As the device is put understress and strain, these conventional stents must find regions ofgreater pliability within the strut matrix. These strut regions absorbthe load throughout the system and under periods of repeated externalforces begin to fail, such as through metallurgical friction loading.

The single column configuration of the tack 10′ is not subject torepeated weak point loading due to movement of remote stent portionsbecause the tack does not have to be axially elongated to provideeffective tacking treatment. Other benefits that derive from theshortness include reduced friction at the interface with the cathetersheath during delivery and with the blood vessel wall. As discussedabove, the stress at the blood vessel wall interface is reduced due tothe lack of cell-to-cell dragging or pulling which in turn reduces thepotential that the tack will pull or drag adjacent cells increasingcellular inflammation or histological response along the lumen wall. Asingle column or other axial short configuration also reduces the stressalong each strut because the overall length of single column or otheraxial short structures or configurations are less affected by theanatomical motion (e.g., bending, twisting, and rotating). This results,at least in part, from the anatomy shifting around short structureswhile longer structures do not allow the anatomy to shift and thuslonger structures absorb more forces resulting from this anatomicalmotion.

Any motion between the surfaces of the tack and the blood vessel cancause rubbing and friction. If the motion is very small it can bedescribed as micro-rubbing, as discussed above. Even micro-rubbingproduces a negative effect on both the tack 10′ and the biological cellsof the blood vessel. For example, friction occurs when a portion of animplanted object moves while another portion is stationary or moving bya smaller amount. Differential amounts of moving over time weakens thematerial leading to fracture by processes such as work hardening. Thebiological cells become irritated by the friction and can respond byproducing an inflammation response Inflammation can drive a variety ofundesired histological responses including neointimal hyperplasia andrestenosis.

2. Controlled Angle of Struts

FIG. 5C shows that the tack 10′ has two circumferential members or rings12 which each have a plurality of internal angles, including α, and σ. Afirst angle α is defined at the first outward apex 24 between the struts26, 27 and a second angle σ is defined at the second outward apex 25between the struts 28, 29. In some embodiments, the first angle α can begreater than the second angle σ. For example, the first angle α can bebetween 43° and 53°, or between 45° and 51°. The second angle α can bebetween 31° and 41°, or between 33° and 39°. In some embodiments, thefirst angle α can be about 48°, and the second angle σ can be about 36°.

In a preferred embodiment, the tack 10′ has an expanded outer diameterof 7.5 mm and the first angle α can be 47.65° and the second angle σ canbe 35.56°. In such an embodiment, the plaque tack 10′ can be formed froma tube stock with an initial outer diameter 4 mm. The tube stock can beexpanded to 7.5 mm and then heat treated in that shape. In someembodiments, the plaque tack 10′ can be made of a shape memory materialand the heat treatment step can be to engrain that particular shape intothe “memory” of the material. The plaque tack 10′ can then be crimped orcompressed and flash frozen in the compressed state to then be loadedonto a delivery device.

A beneficial feature of the tack 10′ is that the angle of the struts asthey meet at each apex can be controlled in at least one of an expandedand a contracted state. For example, the internal angles α, σ of theoutward apices 24, 25 can be controlled to be within ±5% of a selectednominal value. This control can be achieved for example, in the expandedstate during the heat treatment during the manufacture of the plaquetack 10′.

It has been found that control of the angles can beneficially offerrelief from imperfections in the manufacturing process. In some cases,the control of other dimensions can be relaxed if these angles aresufficiently well controlled. By controlling these angles, productionrun quality can be improved. Such control has been found to enablerepeatable, uniform, and balanced compressibility of the tack 10′ duringthe crimping cycle of manufacturing. These factors increase productionrun repeatability and offer ease of volume manufacturing which resultsin a reduction in overall cost of the part.

In addition, control of the apex angles allows the plaque tack 10′ tobetter distribute stresses along the circumferential members or rings12. The control of apex angles can be used to control or distributestresses within the ring 12, e.g., uniformly along the length of thestruts or non-uniformly to a region that can more robustly respond tostress loading. By distributing stress along the strut, the problematiclocalized stresses on the tack 10′, such as at vulnerable spots can beavoided during the expansion and crimping processes of manufacturing.

3. Inverse Tapering Struts

In some embodiments, such as that shown in FIGS. 5A-C, the width of oneor more of the struts 26, 27, 28, 29 of the tack 10′ can be different atdifferent locations, e.g., can vary along the struts. For example, thestruts can be tapered along their length. The taper can be the same ordifferent along each strut or along each type of strut. For example,each circumferential member or ring 12 can be made up of a pattern ofrepeating struts, with each type of strut having a particular taper.

FIG. 5C shows that the ring 12 has a first strut coupled with a bridge14 that is tapered such that a portion of the strut closer to themidline C (sometimes referred to herein as a medial portion or location)is narrower than a portion of the strut spaced farther away from themidline C (sometimes referred to herein as a lateral portion). A secondstrut is connected to the first strut at lateral ends of the first andsecond struts. The second strut can have the same or a different taper.For example, the second strut can also have a medial portion narrowerthan a lateral portion of the second strut. In addition, the secondstrut can be narrower overall than the first strut. A third strut can beconnected to the second strut at medial ends of the second and thirdstruts. The third strut can have a medial portion that is wider than alateral portion thereof. A fourth strut can be connected to the thirdstrut at lateral ends of the third and fourth struts. The fourth strutcan have a medial portion that is wider than a lateral portion thereof.The fourth strut can have the same or a different taper from the thirdstrut. For example, the fourth strut can wider overall than the thirdstrut.

FIG. 5C schematically illustrates the differences in the widths of thestruts in one embodiment. In some embodiments, the long struts 26 andthe long strut 27 have the same width at the same axial position and theshort struts 28 and the short strut 29 have the same width at the sameaxial position. The struts 26 and the strut 27 can have the same shape.The strut 28 and the strut 29 have the same shape in some embodiments.The shape of the struts 26, 27 can be different form the shape of thestruts 28, 29. In some embodiments, the long strut 26 and the long strut27 have different widths at the same axial position and the short strut28 and the short strut 29 also have different widths at the same axialposition.

In a preferred embodiment, the long struts 26, 27 are disposed at afirst circumferential location of the tack 10′ adjacent to one of themarkers 22. In particular, the strut 26 has a medial end connected to orforming a portion of one of the inward apices 18 and a lateral enddisposed away from the inward apex 18. The lateral end is coupled to thestrut 27 at or adjacent to the outward apex 24. The strut 26 has a widthW4 adjacent to the medial end and a width W2 adjacent to the lateralend. In this embodiment, the width of the strut 26 increases along thelength thereof from the width W4 to the width W2. The increase in widthalong the strut 26 preferably is continuous along this length.

Also, the sides of the struts 26 can be sloped relative to alongitudinal axis L_(A) of the strut 26. For example, a first side 48disposed between the longitudinal axis of the strut 26 and the strut 27can be disposed at an angle to (e.g., non-parallel to) the longitudinalaxis of the strut 26. In another embodiment, a second side 46 of thestrut 26 can be disposed at an angle to (e.g., non-parallel to) thelongitudinal axis of the strut 26. In one embodiment, both the first andsecond sides 46, 48 of the strut can be disposed at angles to thelongitudinal axis of the strut 26.

The strut 27 preferably also has different widths at different pointsalong its length. In particular, the strut 27 can be wider in agenerally lateral direction adjacent to the outward apex 24 than it isadjacent to the inward apex 19. As discussed above in connection withthe strut 26, the strut 27 can have side surfaces that are angledrelative to the longitudinal axis of the strut 27. The strut 27 can betapered between its ends, e.g., having a continuously decreasing widthalong its length from wider adjacent to the outward apex 24 to narroweradjacent to the inward apex 19.

The strut 28 extends from the strut 27 or inward apex 19. The strut 28can have a medial end that is wider than a lateral end of the strut 28and can have different widths at different points along its length. Theside surfaces can also be angled relative to the longitudinal axis ofthe strut 28.

Finally, a strut 29 can be connected to the strut 28 or outward apex 25at a lateral end of the strut 29. The strut 29 can have a medial endthat is wider than the lateral end thereof. The strut 29 can have ataper that is the same or different from the strut 28. For example, thestrut 29 can be wider overall than the third strut.

In one embodiment, the strut 26 can have a width W₂ of about 0.12 mm atthe lateral end near the outward apex 24 and a width W₄ of about 0.095mm at the medial end near the inward apex 18 and the strut 28 can have awidth W₆ of about 0.082 mm near the outward apex 25 and a width W₈ ofabout 0.092 mm near the inward apex 19. More generally, the change inthickness between W4/W2 expressed as a percentage can be between about70% and about 90% more typically between about 75% and about 85%, and incertain embodiments about 80%. The tapering can also be inverted, e.g.,with the struts tapered from the ends (e.g., lateral edges) toward themedial portion.

FIG. 5E illustrates another variation in which the width of one or moreof the struts of the tack can be different at different locations, e.g.,can vary along the struts. For example, a strut 27′ can be provided thatis similar to the strut 27 except that the strut 27′ is narrowest in amid-section N. The strut 27′ can have a lateral wide portion L adjacentto the outward apex 28 and a medial wide portion M adjacent to theinward apex 18. The width of the strut 27′ reduces along the lengththereof from the lateral wide portion L toward the medial portion M. Inone embodiment, the strut 27′ is continuously narrower along the lengthfrom the lateral end of the strut 27′ toward the midline of the strut.The strut 27′ can be narrowed such that the ratio of width at themidline to width at the lateral end of the strut 27′, expressed as apercentage, is between about 20% and about 85%. In some embodiments,this percentage is between about 35% and about 75%. The tapering can besuch that this percentage is between about 55% and about 70%. From themedial wide portion, the strut 27′ can be narrowed along the lengththereof. In one embodiment, the strut 27′ is continuously narrower alongthe length from the medial end of the strut 27′ toward the midline ofthe strut. The strut 27′ can be narrowed such that the ratio of width atthe midline to width at the medial end of the strut 27′, expressed as apercentage, is between about 20% and about 85%. In some embodiments,this percentage is between about 35% and about 75%. The tapering can besuch that this percentage is between about 55% and about 70%. Theembodiment of FIG. 5E provides a greater range for compression andexpansion in smaller diameter configurations. Smaller diameterconfigurations can be used in smaller body lumens, e.g., blood vessels.For example, a tack with this configuration can be formed out of 2.3 mmdiameter tubing, whereas the embodiments of FIG. 5C are optimally formedout of 4.5 mm diameter tubing. The configuration of FIG. 5E can be usedto make tacks that are suitable for a 4 French delivery device. Tacksconfigured as in FIG. 5E can have an unconstrained expanded size ofbetween about 4.5 mm and about 6.5 mm. In some embodiments, devicesincluding the configuration of FIG. 5E can have an unconstrainedexpanded size of between about 5 mm and about 6 mm, e.g., between about5.5 and about 6.0 mm. One embodiment expands to about 5.7 mm whenunconstrained.

A unique inverse taper or variation in width along the strut is achievedby inverting the orientation of the taper between the short struts 28,29 and the long struts 26, 27. The longer struts 26, 27 go from a narrowwidth near the inward apices 18, 19 to a broader width near the highoutward apex 24. Conversely, the shorter struts 28, 29 are the oppositewith a broader width near the inward apices 18, 19 to a narrower widthnear the low outward apex 25.

Through strategic selection of the width of the struts, as discussedabove, the plaque tack can distribute the stresses observed duringcompression and after deployment. This feature can also contribute tothe control of the stress by distributing the region of stress moreuniformly along the length of the strut. In some embodiments, it may bedesirable to distribute the stress non-uniformly to regions more able tohandle the stress.

4. Dual Amplitude Struts

As been discussed above, the ring 12 illustrated in FIGS. 5A-5C has anundulating sinusoidal pattern. The axial extent of the ring 12 can varyabout the circumference of the ring 12, for example providing aplurality of amplitudes as measured by the distance from an inward apexto an adjacent outward apex. The undulating pattern can have one or moreamplitudes, such as the dual amplitude configuration shown. In the dualamplitude configuration the plurality of struts 26, 27, 28, 29 extendbetween inward 18, 19 and outward apices 24, 25.

In some embodiments, the outward apices 24, 25 alternate between a highoutward apex 24 and a low outward apex 25. In this context “high”corresponds to a larger distance H1 as measured from a central zone ormidline C of the tack 10′ and “low” corresponds to a smaller distance H2as measured from the midline C (FIG. 5C).

The varying amplitude of the long and short sinusoidal struts describedabove can provide additional control of the plaque tack's functionality.In particular, it can enhance compression of the tack 10′ to provide agreater change in circumference from the fully expanded configuration toa compressed configuration when crimped during manufacturing. Greatercompressibility facilitates delivery in smaller vessels and a greaterrange of indication that can be treated because it enables a smallercrossing profile delivery system.

The height H₁, H₂ of the apices is measured from the center line C tothe top of the respective outward apices 24, 25. The dual amplitudesinusoidal patterned plaque tack 10′, such as that shown in FIGS. 5A-C,enables broad ranging conformable dimensions that can easily be scalableto different outer diameter designs. The open cell single column designallows broad range compression and expansion. This is partly due to thelength of strut available for effective expansion. The ease ofcompression is associated with the position of the apices disposed H₁and H₂ from the center of the tack, which permits these apices tocompress at a different locations instead of at the same laterallocation. If H₁ and H₂ of the apices are aligned (e.g., at the sameaxial location) they would press against each other during compressionlimiting the compression range.

The ranges of compression for the plaque tack 10′ have been measured to0.25 times nominal tube size in combination with ranges of expansion upto 2 times nominal tube size, although these are not the anticipatedlimits of the device. Combining these ranges the full range ofcompression has been measured at 0.125 times the heat treated outerdiameter. As discussed above in SECTION II.B.2, in some embodiments thenominal tube size is 4.5 mm and the tube is expanded to 7.5 mm in themanufacturing process. According to some embodiments, the distance fromthe midline C of the device to the apex of the longer struts H₁ isapprox. 3.0 mm, while the distance H₂ to the apex of the shorter strutsis approx. 2.6 mm.

In addition to the enhanced compressibility range, the energy stored inthe shorter amplitude struts offers additional control of the plaquetack 10′ during the release phase of delivery within the blood vessel.As the catheter sheath is retracted, the longer struts are uncoveredfirst followed by the shorter struts (FIG. 5C). This mismatch providesgreater retention forces to maintain the plaque tack 10′ in the deliverycatheter and thus provides greater control of the plaque tack duringdelivery.

5. Centrally Disposed Anchoring and Elevating Structure

FIGS. 5A-5C illustrate that the plaque tack 10′ can include centrallydisposed anchors 20. While the anchors 20 are primarily for securingloose plaque, as discussed above, their placement and configurationenhance the control of the deployment and the performance of the tack10′ once placed inside the blood vessel.

As discussed above, the plaque tack 10′ can be a self-expandingcircumferential structure and the anchors 20 can be disposed on an outerportion of the tack. The anchors 20 can be coupled with any portion ofthe tack 10′ but preferably are disposed adjacent to the midline C ofthe bridges 14 as discussed above. In one embodiment, the tack 10′includes two anchors disposed on either side of the midline C asillustrated in FIG. 5C. In another embodiment, a single anchor can beprovided on the midline C. In a further embodiment, at least threeanchors 20 can be provided, such as one on the midline and two on eitherside thereof as illustrated in FIG. 5C. The bridge 14 can have twoanchors on one side and one anchor on the other side connecting the twoother anchors, as shown in FIG. 5D. In FIG. 5D, an anchor 20′ is locatedat the center of the tack 10′ along its axial direction. This embodimentprovides at least one anchor 20′ that is located on both sides of themidline C. Also, the anchor 20′ can be located on an opposite side ofthe marker 22 from the anchors 20. As such, plaque can be anchored froma plurality of directions, e.g., a plurality of circumferentialdirections. In a further embodiment, the anchors 20 are not present anda single anchor 20′ located on the midline C is provided. The embodimentillustrated in FIGS. 5A-C could also be modified to include one or moreanchors on either side of the marker 22, where anchors are currentlyonly shown on one side.

In one aspect, the plaque interaction of the tack 10′ is primarilyprovided by the anchors 20 and to a lesser extent the bridges 14. Insome embodiments, the anchors can have a preferred penetration lengthinto the plaque of 0.01 mm to 5 mm. In certain variations, thepenetration length is within a range of about 0.03 mm to about 1 mm. Inother variations, the penetration length is within a range of about 0.05mm to about 0.5 mm. The bridges 14, which can be disposed at alternatinginward apices, as discussed above, can be configured to reside on atangential plane of a cylinder when the tack 10′ is fully expanded andnot being deformed by an outward structure. The tangent configurationcauses the anchors 20 to project outward toward from the cylindricalsurface of the tack 10′. In this outward projecting position, theanchors are adapted to engage plaque or other vascular deposits causingthe vessel to vary from its unobstructed fixed state, e.g. to beout-of-round.

The tangential projection of the anchors and bridges also advantageousenhances the control of the tack 10′ upon deployment. A technique fordeploying the tack 10′ involves positioning the tack in a hollowcatheter body. When positioned in the catheter body, the tack 10′ iscompressed to a compressed state. The rings 12 are highly conformal dueto their construction, discussed above. As a result, the rings fullyappose to the inner luminal surface of the hollow catheter body. Incontrast, the bridges 14 and anchors 20 are more rigid and therefore areless conformal and as a result bite into the inner luminal surface ofthe catheter body. This creates a retention force within the catheterand limits unintended movement of some or all of the tack 10′ toward acatheter deployment zone.

In some embodiments, the retention force of the barbs 20 is maintainedor increased after partial deployment of the tack 10′. In particular, aregion of relatively high flexibility can be provided at the junction ofthe bridges 14 and the rings 12. While high flexibility sections ofstents can be areas of concern, such is not the case in the plaque tack10′ for reasons discussed below. The flexible region can have anymaterial property or structure to enhance its flexibility at leastcompared to that of the bridges 14 such that upon movement of the ring12 on the leading edge of deployment, the tangential configuration andtendency of the anchors 20 to bite into the hollow elongate catheterbody is not diminished. Such is the case even though the leading edgering 12 may expand to at least one-half of its fully expanded size.

As shown, the bridge 14 is connected to each ring at the inward apex 18where at least a portion of the bridge 14 can be aligned, partially orsubstantially aligned with one of the struts that make up the ring 12 ashas been described. For example, as shown, the bridge 14 is aligned witha high amplitude sinusoidal section of the pattern. The region ofrelatively high flexibility can be disposed between the inward apex 18and the bridge 14.

In certain embodiments, expansion of the ring 12 may even cause theanchors 20 to rotate outward to increase the retention force in thecatheter body. For example, expansion of the strut 26 may cause aninward deflection of the inward apex 18. While ring 12 is expanding aslight rotation of anchors 20 may occur which may cause a torquedoutward deflection of the leading anchor and a corresponding torquedoutward deflection of the trailing anchor. With reference to FIG. 5C, ifthe depicted ring 12 is first expanded upon moving out of the hollowcatheter body, the anchor 20 to the right of the midline C may bedeflected inwardly toward the central axis of the catheter body but theanchor to the left 20 will be deflected outward to increase theretention force thereof. Thus, the plaque tack 10′ may be retained inthe catheter during such partial expansion. Due to this feature theplaque tack 10′ can be uniformly placed, as discussed further below inSection II.B.8.

The out-of-cylinder nature of the bridges 14 and anchors 20 also providebenefits to the deployed state. In particular, in some embodiments in anexpanded state, the plaque anchors 20 are disposed radially outwardly ofa cylindrical surface formed by the rings 12. The degree ofout-of-cylinder can depend on the application, but in general may besufficient to space at least a portion of the cylindrical surface fromthe inner walls of the vasculature when deployed. As such, the anchors20 or the anchors combined with the rings 12 can be configured as focalelevating elements, which are discussed below in SECTION III.

As the plaque tack 10′ expands within a blood vessel, the struts willengage the vessel wall and/or plaque. It is anticipated that in mostsituations, at least some of the struts will be deformed in response toirregularities of shape within the blood vessel. At the same time, thebridges 14 are less deformable and thus will resist such deformationretaining a circular configuration. The outward forces that are appliedby the strut members are transferred into those areas that are incontact with the blood vessel wall. In some cases, when the tack 10′conforms to an irregularly shaped blood vessel lumen, the rigid centralanchors become the region for blood vessel contact. The cumulativeoutward force of the struts in the rings 12 are applied through thebridges 14 to the anchors. Adjacent struts share their load with thecontact region pressing the blood vessel into an enlarged configuration,such as a conformed circle.

Such a configuration can provide benefits such as helping the plaquetack 10′ to remain in place after delivery and allowing the plaque tack10′ to respond dynamically to the movement and pulsing of the bloodvessel itself. In addition, this configuration can have the benefit ofreducing cellular response and device fracture by limiting strut fatigueand associated micro friction loading at the tack-blood vesselinterface.

In some embodiments, the bridge 14 can include one or more anchor. Insome embodiments, the bridge can be formed entirely of anchors.

After deployment of the plaque tack 10′, the surgeon has the option ofplacing an angioplasty balloon at the site of the tack and inflating theballoon to press the anchor or anchors 20 into the plaque and/or wall ofthe blood vessel.

6. Flat Midline Markers

As discussed above, the plaque tack 10′ has one or more markers 22. Inone embodiment, a series of radiopaque markers 22 can be located on thetack 10′. In some embodiments, the radiopaque markers 22 are at themidline C of the device. The radiopaque markers 22 can be disposedbetween the two circumferentially oriented sinusoidal members or rings12.

In some embodiments, the radiopaque markers 22 (e.g., platinum ortantalum) can be disposed adjacent to the plaque anchors 20. Theradiopaque markers 22 can have one of many different shapes orconfigurations. In some embodiments, the radiopaque markers 22 have aplanar or flat structure. As shown in FIG. 5C, each marker 22 is coupledwith, such as by being press-fit or riveted into, a circular eyeletproducing a flat leveled surface with the eyelet. The markers 22 offerclear visibility of the tack 10′ in the catheter delivery system andprovide guidance to the clinician for accurate placement during theprocedure.

According to certain delivery methods, due to the co-placement of theanchors 20 and the markers 22 at the bridges 14 between the sinusoidalrings 12, the markers 22 can offer a visible clue to the clinician ofthe point when the release of the device will take place. For example,once the markers 22 meet a marker strip located at the tip of a deliverycatheter sheath the full device can be deployed.

7. Simultaneous Device Placement in the Vessel

The plaque tack 10′ can be configured for simultaneous placement withina blood vessel. Simultaneous placement of the plaque tack 10′ can bedefined as the entire plaque tack 10′ being released from the deliverycatheter prior to any all of the distal apices of the plaque tack 10′contacting the blood vessel lumen where it is to be placed. This eventcan occur when the anchors 20 are completely uncovered by the cathetersheath allowing the entire plaque tack 10′ to expand against the lumenwall of blood vessel. The struts 26, 27, 28, 29 can be free floating,e.g., spaced from the vessel wall or applying negligible force to thewall, such that they do not contact the lumen wall prior to simultaneousplacement. For example, the anchors 20 may have the effect of spacing aportion or substantially all of the struts 26, 27, 28, 29 from thevessel wall. Other forms of focal elevating elements are discussed belowthat can be used to space the tack 10′ from the lumen wall.

Simultaneous placement offers the clinician the ability to controlplacement up until the markers 22 and/or anchors 20 are uncovered whichcan generate a full expansion event (struts adjacent to or contactingthe lumen wall). In some embodiments, the full expansion event does notoccur until the anchors 20 are uncovered due mainly to internal forcesof the tack 10′ urging the anchors 20 to engage the delivery sheathdescribed above.

Another benefit of simultaneous placement is the reduction of anyinadvertent dragging or pushing of struts against or along the lumensurface during the placement of the plaque tack 10′. Due to thecomplexity and variation of disease, location of placement, anddissections morphology, the ability of the outer surface of the plaquetack 10′ to contact the lumen wall all at the same time is dependant onthe deployment circumstances. However, the ability of the plaque tack10′ to contact the lumen wall completely upon release from the cathetersheath within fractions of a second has been observed.

8. Low Slope Force Curve

Another unique aspect of the plaque tack 10′ is that it can beconfigured with a force curve with an extended area having a low slope.A force curve, such as that illustrated in FIG. 6A, shows the amount ofexpansive force exerted by a self expanding plaque tack 10′ or stentwhen moving from a compressed state to an expanded state. The expansionforce of a device can be a factor in choosing the correct device to beplaced in a particular blood vessel.

Still referring to FIG. 6A, the force curves of a SMART stent (i.e., aS.M.A.R.T.® Control transhepatic biliary stent by Cordis Corporation),another conventional stent, and a plaque tack having the wall patternillustrated in FIG. 5A. The chart shows the radial force in Newtons (N)on the y-axis and the outer diameter of the device in millimeters (mm)on the x-axis. As the device is expanded or moved from the compressedstate to the expanded state, the outer diameter increases. Because thedevices are self expanding, they have a set amount of stored potentialenergy. When released, the potential energy is converted into kineticenergy as the internal forces try to restore the device to its expandedshape. The kinetic energy can then have an impact on the blood vesselwhen the device is implanted. Also, if the plaque tack 10′ is not fullyexpanded a generally constant force will be applied to the vessel wallthat corresponds to remaining potential energy stored in the tack 10′.

FIG. 6A shows a first dark line A1 showing the compression of a 7.5 mmplaque tack 10′ from approximately 7.5 mm to approximately 2 mm ofcompressed diameter. After a gradual slope region between about 7.5 mmand about 6 mm, the slope of the force for each incremental reduction indiameter is greatly reduced, providing a narrow band of force requiredto fully compress the tack 10′ from about 6 mm to about 2.0 mm. Thisportion of the force curve is very flat, meaning that the appliedcompression force does not greatly increase as the tack 10′ approachesits fully compressed state. The force curve of the plaque tacks 10′ uponexpansion is illustrated by a dark lines B1 extending from 2.0 mm ofcompressed diameter to about 7.5 mm of expanded diameter. This portionof the curve can be thought of as the working portion, in which theforce on the Y-axis is the force that the plaque tack 10′ would apply toa vessel wall upon expansion. For example, if the plaque tack 10′ weredeployed in a vessel lumen having a bore of about 5.0 mm, the outwardforce of the tack 10′ on the wall would be well under 1.0 Newton (N).Over a range of about 2 mm, the range of outward force is less thanabout 0.05 N+/−about 30%.

FIG. 6A shows in a dimmer line A2 the crimp performance of a SMART stentin a similar test. As discussed above in connection with other prior artstents, the SMART stent is a longer structure than the plaque tack 10′.In particular, the S.M.A.R.T.® stent tested was 40 mm long with a 8 mmunconstrained outer diameter, whereas the tack that was tested was 6 mmlong with a 7.5 mm unconstrained outer diameter. However, it is believedthat the comparison between the plaque tack 10′ and the SMART stentillustrates a difference that would still manifest with a comparablelength version of the SMART stent. As shown on the graph, the line B2has a much higher crimp force in a range from just over 8 mm to about6.5 mm. At about 6.5 mm, the slope of the crimp force decreases and thecrimp force increases at a much slower rate. The outward force at thefully crimped state is much higher. Although the fully crimped state ofthe SMART stent corresponds to a smaller diameter, the crimp force for acomparable diameter is much higher on the SMART stent. Line B2illustrates the working zone of the SMART stent that was tested. Line B2shows the outward force over the range of expansion from about 2 mm toabout 6 mm. As can be seen, the slope of line B2 is much greater at allpoints along its range between 2 mm and 6 mm. The practical effect ofthis higher slope is that the SMART stent is much more sensitive tochanges in the bore size of the vessel into which the expanded plaquetack 10′ is deployed.

As can be seen in FIG. 6A, in some embodiments, a low slope of the forcecurve can be essentially flat over about a 3 mm outer diameter expansionrange. In other embodiments, a low slope of the force curve can be overa 2.5 mm outer diameter expansion range with a change in force of changeless than 1 N. Factors in the ability of the tack to have a broad rangewhere the radial forces change less than 1 N include the midlineanchors, dual amplitude struts, and the varying strut thicknesses,discussed above.

FIG. 6A illustrates another conventional stent having a compressioncurve A3 and an expansion curve B3. The SMART stent is a widely usedstent pattern. The curves A3, B3 represent another conventional stentdesign. Although the curves A3, B3 have lower peak compression force atthe left-hand side of the curve, the slope is still dramatically higherover the range of use than is the tack illustrated by curve A1, B1.

The tack is radially self expandable through a range of at least about 2mm, generally at least about 3 mm and typically through a range of atleast about 4 mm or 5 mm, while exhibiting a radial expansion force ofno more than about 5 N at any point throughout the range. In someembodiments, the maximum radial expansion force throughout the expansionrange is no more than about 4 N and preferably is no more than about 3N. In one embodiment, the tack is expandable over a range of at leastabout 3 mm (e.g., from about 3 mm to at least about 6 mm) and the radialexpansion force is less than about 3 throughout that range. Generallythe change in expansion force will be no more than about 3 N andpreferably no more than about 2 N throughout the expansion range. In oneembodiment, the expansion force drops from no more than about 2 N at 3mm diameter to no more than about 1 N at 6 mm diameter. Typically thedifference between the radial force of compression and the radialexpansion force at any given diameter throughout the expansion range isno more than about 4 N, generally no more than about 3 N, preferably nomore than about 2 N and in one embodiment is no more than about 1 N. Inone implementation, the tack is expandable throughout a range whichincludes 3 mm through about 6.5 mm and the difference between thecompression force and expansion force at each point along thecompression/expansion range differs by no more than about 2 N andpreferably by no more than about 1 N.

In general, the outward force of the plaque tack 10′ is preferred to beas low as possible, while providing sufficient force to hold the plaqueagainst the lumen wall through a wide range of luminal diameters. Whenforce is elevated, e.g., by two to three times the sufficient holdingforce, adverse side effects can occur. These can include irritating thecells of the vessel wall that are in contact with the device, which canlead to re-stenosis. Although a very low force device is preferred forthe typical treatment, higher force devices may be useful where looseplaque is found at calcified lesions.

One advantage to having a slow change in force as the device isexpanding is the ability to predict the energy that the blood vesselexperiences independent of the lumen diameter. Another value would bethe reduction of necessary inventory for hospitals. For instance, it hasbeen found that two part sizes of the tack 10′ shown in FIGS. 5A-C canbe used for plaque tacking treatments in blood vessels locatedthroughout the leg, from hip to ankle. This is believed to be due ingreat part to the tack 10′ having a slope of less than −0.3 N/mm.

C. Plaque Tack Design Parameters

One purpose of the plaque tack described herein, as distinct fromtraditional stenting, is to reduce the amount of implanted foreignmaterial to a minimum while still performing focal treatment of theblood vessel condition so as to cause a minimum of blood vessel wallreaction and adverse post-treatment restenosis. The plaque tack isdesigned to have substantially less metal coverage and/or contact withthe blood vessel surface, thereby inciting less acute and chronicinflammation (See FIG. 6B). Reduced contact area of implanted materialagainst the blood vessel wall is correlated with a lower incidence ofintimal hyperplasia and better long-term patency. Substantially reducedlength along the axial distance of the blood vessel permits a moretargeted treatment, correlates with less foreign body coverage of theblood vessel surface, avoids covering portions of the surface that arenot in need of coverage, and correlates with both early and lateimproved patency of blood vessel reconstructions.

The plaque tack can be deployed only where needed to tack down plaquethat has been disrupted by balloon angioplasty or other mechanisms.Rather than cover an entire area of treatment, the plaque tack can beplaced locally and selectively, for example, not extending into normalor less diseased artery segments (See FIG. 6B). This permits the bloodvessel to retain its natural flexibility because there is minimal to noscaffolding when a small profile tack is used locally or even whenmultiple tacks are spaced apart over the area of treatment. Stillfurther reduction in the pressure profile can be achieved by using“points-of-contact” to achieve higher pressure at focal points andlifting the neighboring strut section away from the blood vessel wall toreduce the overall load of the outward pressure elsewhere on the tackstrut structure.

One parameter for design of a plaque tack is having a tack axial lengthto expanded diameter (L/D) ratio of no more than about 2.0, often nomore than about 1.5 and in some implementations no more than about 1. Inone embodiment, the tack has about an L/D ratio of 0.8. That is, thelength of the tack along the axis of the blood vessel is about equal toor less than the expanded diameter of the tack. The preferred plaquetack is thus shaped like an annular ring or band, whereas the typicalstent is shaped like an elongated tube. The small-profile tack can thusbe used locally for targeted treatment of disrupted regions of the bloodvessel surface with a minimum of foreign material coverage or contact.Tests show that a plaque tack with an axial length/diameter ratio 1causes almost no biological reaction or subsequent blood vesselnarrowing in comparison to a traditional stent where the axial length isgreater than the diameter, and usually much greater. Tests indicate thatdevice L/D1 results in a reduction in scaffolding much less than that ofthe typical stent and causes less arterial wall reaction. Forapplication at sites of small dissection after balloon angioplasty, aplaque tack of minimal footprint may be used such as a single, thinring-type tack with an L/D ratio in the range of 1/10 to 1/100.

Studies on stenting have shown that the axial length of a stent iscorrelated with a tendency for occlusion in multiple vascularterritories. The more stent axial length that has been placed, thehigher likelihood that the reconstruction will fail. The axial length ofa stent is also directly linked to the frequency and tendency of thestent to break when placed in the superficial femoral artery. Themedical literature indicates that the superficial femoral arteryperforms like a rubber band, and it is likely that changes to thenatural elongation and contraction of the superficial femoral arteryplay a significant role in the failure mode of superficial femoralartery stents. In contrast, the small-profile plaque tack can beimplanted only in local areas requiring their use, thereby enabling theblood vessel to retain its natural flexibility to move and bend evenafter the surface has undergone tacking. Multiple tacks may be implantedseparated by regions free of metallic support, thereby leaving theartery free to bend more naturally.

Outward radial pressure exerted on the blood vessel wall can also besubstantially reduced by the small-profile tack design, even whenmultiple tacks are used in a spaced-apart configuration. To minimizethis outward force while still providing the required retention ofdissections against the arterial wall, a series of anchor barbs or focalelevating elements can be utilized. The presence of these featuresapplying focal pressure to the wall of the artery allows the rest of thetack to apply minimum outward force to the artery wall. The points whichapply the pressure can be very focal, and this is where the most forceis applied. The focal nature of the application of the pressure exertedby the tack also minimizes the structural effects of the device.Uniformly distributed anchors or focal elevating elements can provide adistribution of radial energy maximizing the tendency to form a circularlumen.

Another important parameter for design of a plaque tack is the ratio ofVessel Coverage Area (C) to Total Vessel Surface area (TVS). In onedefinition, the value C is the length of the prosthesis (e.g., stent ortack) times the average circumference of the vessel in which it isplaced and the value TVS can be the length of the lesion or arearequiring treatment times the same nominal circumference. This can alsobe simplified to a ratio of total length of the prosthesis when expandedto the nominal circumference divided by the length of the lesion in thevessel. These concepts can be applied to one tack device or when severalspaced-apart tack devices are placed across the length of a blood vesseltreatment area. Where multiple stents or tacks are used, a simplifiedratio could be total non-overlapping length divided by lesion length orcould be the sum of the length of the prostheses divided by the sum ofthe length(s) of the lesion(s). For a plaque tack, the C/TVS ratio is inthe range of about 60% or less, whereas for a stent it can be 100% ormore (if applied to overlap the treatment site).

For a focal lesion, the conventional treated vessel length is X+10 mm to20 mm where X is the length of the lesion and the added length isadjoining on normal or less diseased artery proximal or distal to thelesion. In traditional stenting the entire treated vessel length wouldbe covered with a stent. For example, in the case of a 2 cm lesion, thetreated vessel length would be 3 to 4 cm (usually a single stent of thislength would be selected), so that C/TVS is 150%-200%. In contrast, withtack placement about ½ of X would be covered, and none of the adjoiningnormal or less diseased artery would be treated. For example, in a 2 cmlesion, approximately 1 cm would be covered, so that the C/TVS ratio isabout 60% or less. An advantageous aspect of this innovative approach isplacement of bands only in regions of dissections requiring vasculartacking.

As described previously, in some embodiments, a tack device 10′ isformed with rings or mesh bands 12 connected by longitudinal bridgemembers 14 (FIG. 5A). In the figure, the tack 10′ is shown compressedfor delivery in a blood vessel. When expanded, the diameter of the tackdevice can be about equal to the axial length of the tack device.

FIG. 6B illustrates the use of multiple tack devices which are spacedapart over a length of blood vessel at a treatment site as compared to atypical stent. Preferably, the spacing between tack devices is at leastthe axial length of the tack device. Note that the spacing betweenadjacent tack devices leaves untreated vessel area. A typical stent isshown in the upper part of the figure compared to the use of 6spaced-apart tack devices at the bottom part of the figure. In thisnon-limiting example, the overall length of treatment area is 6.6 cm(the same length of the stent) while each band is shown as 6 mm longseparated by 6 mm spaces. Therefore, the Vessel Coverage Area for thestent is the same as Total Vessel Surface area (=6.6 cm×0.6π, or 12.44cm²) which gives a C/TVS ratio of 100%. For the series of spaced-aparttack devices, C is equal to 6×0.6 cm×0.6π, or 6.78 cm², while TVS is12.44 cm², therefore the C/TVS ratio is equal to 54.5%.

When two or more stents need to be employed over an extended length oftreatment site, it has been a conventional practice to overlap adjoiningstents to prevent kinking between stents. Due to the increased metallattice, the region of overlap becomes highly rigid and noncompliant.This noncompliant doubly rigid region further limits the naturalarterial flexibility and increases the tendency for restenosis. Stentfractures occur more frequently in the superficial femoral artery wherethis bending has a high frequency and are common when multiple stentsare deployed and overlap. Stent fractures are associated with a higherrisk of in-stent restenosis and re-occlusion. In contrast, the plaquetacks are designed to be applied in local areas and not to beoverlapped. Optimal spacing is a minimum of l tack axial length apartfor tacks. This permits the artery to maintain its flexibility, and onlya half or less of the treated length of the artery will be covered withmetal. It should be noted that in the case where restenosis occurs aftertack placement the overlapping of the entire treated length with a stentstill allows the stent to retain its patency. This is due to therepeated pattern of regions where no tacks are placed offering regionsof relief and the artery to flex.

The literature in the industry has noted that important factors in stentdesign may be the ratio of Relative Metal Surface Area (RMS) and thenumber of longitudinal segments in the device structure, for example, aspresented by Mosseri M, Rozenman Y, Mereuta A, Hasin Y, Gotsman M., “NewIndicator for Stent Covering Area”, in Catheterization andCardiovascular Diagnosis, 1998, v. 445, pp. 188-192. More particularly,for a given metal surface area, a higher number of longitudinal segments(each of which is thinner) can reduce the size of the gap betweenadjacent segments, reducing the tendency for prolapse. As adapted fromthe RMS measure, an equation for Effective Metallic Interface (EMI) maybe used to compare the embodiment of the tack device with longitudinalbridging members to a typical stent, as follows:

${EMI} = \frac{\left( {1 + n^{2}} \right)C}{\sum\limits_{s = 1}^{x}\;({lw})_{s}}$

Where x is the number of sections of metal, l is an individual metalsection length, w is an individual metal section width, C is the vesselcoverage area underneath the device (lumen surface), and n is the numberof bridge members longitudinally connected between circumferentiallyoriented segments. The summation found in the denominator can beinterpreted as the total metal surface area. The embodiment of the tackdevice with longitudinal bridging members has an EMI≤10, whereas the EMIof a typical stent would be several times greater. This low EMI is dueto the nature of the tack design having a small foot-print and minimallongitudinal bridges while a stent typically has a large foot-print andwould be a multiple several times that.

To further reduce the EMI through the inclusion of lift-off-bumpfeatures (such as anchors, barbs, or focal elevating elements), animproved EMI_(F) can be obtained for the Tack Effective Metal Interfaceas provided with floating elements (see FIG. 9). EMI_(F) can be definedas:

${EMI}_{F} = \frac{C\left( {1 + \left( {n - n_{F}} \right)^{2}} \right)}{\sum\limits_{s = 1}^{x}\;{\left( {{lw} - {l_{F}w_{F}}} \right)s}}$

Where all variables are the same as those in the EMI equation with theaddition of l_(F) is an individual metal section length that is not incontact with the artery (floating off the artery), and w_(F) is thewidth of the same section. If no floating sections exist then n_(F)=0and l_(F)w_(F)=0 and therefore EMI_(F)=EMI.

The inclusion of metal sections that are floating (floating lengthl_(F), floating width W_(F), and number of floating bridges n_(F))reduces the EMI further which is captured mathematically as a summationwith negative variables in the EMI_(F) equation.

The presence on the plaque tack of lift-off-bump features (such asanchors, barbs, or focal elevating elements) minimizes the pressure ofthe overall structure upon the blood vessel wall by transferringregional outward forces to focal pressure points, thereby applying ahigher pressure at the focal points. The presence of the lift-off-bumpfeatures applying focal pressure to the artery wall allows the rest ofthe tack to apply minimum outward force to the artery wall. Wherever thelift-off-bump features are placed, the outward radial energy ismaximized at that region, producing a slight outward bowing of thearterial wall. The outward bowing can be used for arterial shaping ormolding, for example, 5 or more uniformly distributed focal points canbe used to form a circular lumen. Circular lumens offer additionalbenefit from the standpoint of the vessel wall interaction, independentof the vascular injury.

In any of the embodiments herein described, the plaque tack device maybe made from Nitinol, silicon composite (with or without an inertcoating), polyglycolic acid, or some other superelastic material, aswell as stainless steel, tantalum, a cobalt chromium alloy,bioabsorbable or bioresorbable materials (includingbioabsorbable/bioresorbable metals) or a polymer. The strip of materialcan be created from ribbon, round or rectangular wire or a sheet ofmaterial processed through photolithographic processing, laser or watercutting, chemical etching or mechanical removal of the final shape, orthe use of bottom up fabrication, for instance chemical vapor depositionprocesses, or the use of injection modeling, hot embossing, or the useof electro or electroless-plating. It may be fabricated from metal,plastic, ceramic, or composite material.

The plaque tack device is designed to be inherently self-aligning, i.e.,its mechanical installation can accommodate small misalignments. Byreducing stress in the strut members while gripping the arterial wall inthe center of the design, the tack self aligns with the arteriallongitudinal axis. Design features that offer stress relief and provideuniform distribution of the unfolding struts include narrow spacing ofthe anchors, non-uniformly thick struts, and anchors heads that areangled to reduce device from springing forward during delivery. Asdiscussed above, circumferentially oriented anchors located at eachbridge member offer gripping force with the catheter tip and embeddingfeatures when lying on the artery wall. These design features serve tofacilitate placing the tacks in specific locations within diseased bloodvessels.

III. Improvement of Focal Elevating Elements

FIGS. 7A-D show a plaque tack 10″ that is similar to that of FIGS. 5A-Cexcept as discussed below. In particular, the plaque tack 10″ includes afeature that reduces the amount or character of interactions between theplaque tack 10″ and the vasculature by elevating a portion of the plaquetack 10″ off of the vessel wall when deployed.

In particular, the high outward apex 24′ formed by the struts 26 and 27is bent or turned upwards, or radially outwards, to form a focalelevating element (FEE) 32. FIG. 8 shows a schematic view of the FEE 32.In this embodiment, the high outward apex 24′ is bent to form an anglewith the struts 26 and 27. In this way the FEE 32 can help minimize theamount of the tack 10″ that is in contact with the plaque and/or vesselwall while also localizing the forces at few points to more securelyplace the plaque tack 10″. These as well as additional benefits will bedescribed in more detail below.

A plaque tack devices may be provided with focal elevating elements onthe annular periphery of the device. The focal elevating elements aredistinguished from the anchors and barbs generally having greater plaqueor arterial wall penetration to anchor or stabilize the tack in theblood vessel.

The focal elevating elements may or may not penetrate but still offerregional strut elevation and are preferably placed at apices of strutsor periodically along (e.g., perpendicular to) strut lengths. For bothanchors and focal elevating elements the size of the interface betweenthe tack and the arterial wall is preferably equal to or shorter thanthe strut width in at least one direction. The focal elevating elementscan be similar to anchors but either do not penetrate or penetrate thetissue only slightly, thereby minimizing the amount of material surfacearea in contact with the plaque, and offer a set of relief sections forthe outward pressure of the tack device adjacent to the focal elevatingelements, thereby minimizing the friction generated at the blood vesselwall.

The focal elevating elements can be formed and configured on the annularperiphery of the tack device in a similar manner as described for theprevious tack device embodiments and can include the raised contactsections in addition to anchors or sharp points. The contact sectionscan provide improved tacking characteristics in that they increase thecontact forces at the contact sections by compressing the plaque at thecontact regions and decrease the outward force at the sectionsneighboring the focal elevating element. This offers regional pressurerelief in some sections and increase contact pressure at the bumps orsharp points collectively offering a reduction in trauma and cellularresponse of the blood vessel wall.

Because the tack device is held in place by its own pressure exerted onthe blood vessel surface, it is susceptible to friction, includingslight movement between the device and the vessel surface. Every timethe organ moves (e.g., the leg during ambulation), the artery moves. Itcan be inferred that when the artery moves the working device sittingwithin the artery also moves but not necessarily every point of contactmoves in synch with each other. Whenever there is even a small mismatchin movement between the artery and the device the artery and device rubagainst each other promoting cellular reaction and device failure. Ithas been deduced from experimental that this rubbing may irritate theendothelium causing an inflammatory response. In some embodiments,strategically placed focal elevating elements (FEEs) are implemented toreduce the overall regional friction load (thought to be a source ofinflammation, cellular proliferation, and the healing response thatleads to restenosis) of the area being held open.

As an example, a blood vessel such as the popliteal that is cyclicallyshortened and elongated is believed to have a cellular or tissuestructures that elongate and compress in a direction parallel to theaxis of the vessel. The natural behavior of this cellular or tissuestructure involves a significant amount of local movement along thisaxial direction. If an implant to be placed in such a vessel is designedto contact the vessel wall in a direction transverse to this axialdirection, the natural behavior of these tissues or cells will begreatly disrupted. For example, the tissue will be constrained and thenatural movement will be greatly reduced. Also, rubbing can occur alongthe edges of the transversely contacting structure, resulting infriction and/or abrasion of the tissue and corresponding inflammation.FEEs, in contrast, reduce the disruption of the natural behavior of thetissue or cells. If incorporated into a tack device or other prosthesis,FEEs can focus the contact at zones that are spaced apart along adirection transverse to the predominant direction of motion (e.g., theaxial direction in the case of the popliteal or similar vessel). Betweenthese zones of focused contact corresponding to the FEEs, theinteraction of the compressing and elongating tissue or cells with thestructure of the implant is greatly reduced. In this in-between zone,the motion between the compressing and elongating tissue or cells canapproach that of the tissue or cells before the implantation of theprosthesis. Raised sections produced by the FEEs limit the histologicalresponse of the tissue and also the fatigue of the device by limitingthe contact between the device and the tissue.

Independent of the overall amount of contact and number of FEEs, thetack devices smooth the lumen wall, and allow more natural vesselmovement. Where FEEs offer the greatest value is in their ability toreduce the amount of interaction between tissue or cells that move,elongate or compress, which can produce rubbing or friction to suchtissue or cells. It is this highly localized movement or“micro-movement” that increases the cellular response of the bloodvessel surface to the foreign device.

The focal elevating elements are designed to reduce effective metalinterface (EMI) by minimizing the overall material contact with theblood vessel surface. The focal elevating element (FEE) is preferablyconfigured as a narrow, lifted feature with enough height to liftadjacent strut sections of the tack device off from contact with thearterial wall in order to reduce the surface area of foreign material incontact with the arterial wall. Reducing the contact burden is ofparticular value when the strut members are connecting circumferentialrings or circumferentially oriented strut bands. Strut sections orientedagainst the natural grain of the cellular orientation that are incontact with the blood vessel walls can produce microfriction when theymove or rub against the blood vessel walls. By reducing the foreignmaterial contact area against the blood vessel wall, the tendency forproduction of microfriction contact is reduced.

Referring to FIG. 9, a schematic diagram illustrates some of the designassumptions for the use of focal elevating elements on a plaque tackdevice. In the figure, h refers to the height of the focal elevatingelement that is extended out of the blood vessel (note: the penetrationdepth of the focal elevating element that is anchored into the artery orplaque body is not included in this calculation), w refers to the widthof the focal elevating element (at its base), and l_(F) refers to theadjacent strut surface lifted off the arterial wall (mathematicallysimplified as a straight line). The struts adjacent to the focalelevating element may be fabricated with shape memory materials ordesigned as a compression wave providing compensation for lumen diametervariations. The strut forces adjacent to the focal elevating elementsproduce an outward bowing of the struts produced by the forces of thestruts wanting to expand until they are in contact with the blood vesselwall. l_(A) refers to the length of arterial wall that is kept out ofcontact with any adjacent strut structure by the focal elevatingelement.

One or more of the features labeled in FIG. 9 can be varied to provideadvantageous FEE performance. For example, h can vary depending on thesize of the delivery catheter for instance a 4 Fr provides a h of up to150 um. In certain embodiments, a tack with FEEs configured for deliveryin a 4 Fr catheter can have h of about 100 um or less. An exampleembodiment that can be deployed with a 4 Fr delivery system has one moreFEEs with h of about 75 um. Larger tacks with FEEs, e.g., configured fordelivery in a 6 Fr catheter can have an h of up to about 300 um and insome cases 225 um or less. An example embodiment that can be deployedwith a 6 Fr delivery system has one more FEEs with h of about 200 um.Still larger tacks with FEEs, e.g., configured for delivery via a 8 Frcatheter, could have an h of up to 950 um while in certain embodimentsFEEs of up to 500 um could be provided. An example embodiment that canbe deployed with an 8 Fr delivery system has one more FEEs with h ofabout 400 um.

Any of the foregoing dimensions of h may be combined with a variety ofdimensions of W of the FEE. The W dimension would typically be the widthof the strut but could be as little of 50% the strut width and may bebetween about 50% and about 100% the width of the struts at the locationof the FEE. I_(f) and I_(a) are a function of W, the radial force of thesystem, the topography of the lumen, and the delivery device, e.g.,varied if a balloon is used to press the device into the artery. If wejust look at W (non elastic system) then I_(a) may be about equal to thelength of the strut. As outward force (both from the elastic nature ofthe metal and the balloon assist) increases then I_(a) can be reduced,approaching 0. However, in various embodiments, I_(a) is at least about20 um.

The focal elevating elements may be formed as cylindrical, rectangular,linear, spherical, conical, tear dropped, pyramidal, or inclinedelements on the annular periphery of the tack device. They can be formedby bending or stamping a section of the tack structure, by an additiveprocess (such as by welding or annealing on a peripheral surface), by asubtractive process (such as by grinding or etching away surroundingmaterial so that the bump element is higher than the surroundingsurface), or by modifying small sections of the peripheral surface to behigher than the surrounding surface before or after sheet or tubecutting. For example, one method of modification of small sections of amesh tack structure is by knotting, twisting, bending or weaving smallsections of the wire mesh to produce raised elements from the meshsurface which are the interface with the artery wall of the tackdevices.

Properly oriented and symmetrically positioned focal elevating elementscan provide foci for expansion force. As the device exerts outwardforces and the artery exerts inward forces, the focal elevating elementscan be positioned at strategically located positions reducing theoutward pressure of strut sections neighboring the focal elevatingelements.

Both anchors and focal elevating elements can offer strategic advantagesthat include: the reduction in pressure burden across the tack struts byreducing the contact area and translating the outward forces to theanchors and focal elevating elements, minimizing surface contact whichoffers a reduction in the tendency of frictional loading driven by micromovement between the arterial wall and the tack strut, and thestabilization of anchoring the tack where the anchor or focal elevatingelement penetrates the vessel wall a fraction of the features height.

Because the tack device is held in place by its own outward forcepressure exerted on the plaque and blood vessel surface, it may besusceptible to friction, i.e., slight movement between the device andthe vessel surface. FIG. 10 illustrates the forces at play between thetack's focal elevating elements and the arterial wall. F_(T) is thecircumferential force exerted by the tack device against the arterialwalls force, F_(A). F_(FEE) is an additive circumferential force at thefocal elevating element generated by the design and material choice andF_(F) is the frictional force of the artery generated when the arterychanges its orientation or shape due to body forces. Every time a bodyparty moves, the blood vessels move slightly as well. The focalelevating elements can be strategically positioned to reduce localfriction loading which may cause inflammation, cellular proliferation,or bodily response that leads to restenosis.

The number and locations of focal elevating elements can affect theoverall Relative Metal Surface Area (RMS) which was explainedpreviously. The focal elevating elements may be positioned along thelengths of the tack device surfaces such that a minimal amount of metalsurface area is in contact with the artery wall. Focal elevatingelements placed at bridges between circumferential strut rings or at theapices of strut sections of the tack device can offer a majority ofarterial injury relief. When focal elevating elements are placed only atapices and bridges, the RMS of the strut members making up theconcentric ring changes a little while the RMS of the bridges is reducedmore significantly, due to the narrow length, offering relief ofrelative motion of the circumferentially oriented strut rings.

FIGS. 11 and 12 illustrate the use of focal elevating elements on a tackdevice of the type described above with respect to FIGS. 5A-C having twoor more concentric ring sections joined by bridges in between. FIG. 11shows a cell of two adjacent ring sections 290 a and 290 b with strutsections 290 c and which are joined in the middle by bridges 290 d. FIG.12 shows the ring sections expanded under expansion force and opposingsets of focal elevating elements 290 e deployed on opposite ends of thetwo adjacent ring sections 290 a and 290 b. An inset to the figure showsthe round elevating element having a height raised from the strutsurface.

FIGS. 13 and 14 illustrate a cell of another variant of focal elevatingelements formed on a tack device having two or more concentric ringsections 300 a, 300 b joined by bridges 300 d in between. In this cellvariant, the focal elevating elements 300 e are formed by bending thesections of the strut (illustrated as the strut apex) out of thecircumferential plane into varying degrees of tilt such as position “a”,or position “b”, up to a 90 degree vertical orientation shown inposition “c” to form the elevating element.

Inherent in the use of shape memory alloys for the tack devices is theability to conform to the shape of the blood vessel walls. Because thefocal elevating elements can exert an expansion pressure on the bloodvessel walls with a minimal risk of injury, they can be designed toreshape the blood vessel walls to a desired shape. FIG. 15 illustratesthe focal elevating elements (FEE) positioned in diametrically oppositepositions and formed with an extended height to reshape the artery wallsinto an ellipse cross-sectional shape which may better match thearterial cross section (such as an arterial branch) or expand the lumento be more open in plaque-free areas.

FIG. 16 shows a side view of FEEs spaced along a strut length having asmall area lifted off the arterial due to the height of the FEE liftinga short distance of the neighboring strut length. Outward forcesgenerated by the design or material used allow for only a small sectionon either side of the FEE to be lifted off the blood vessel wall.

FIG. 17 illustrates a perspective view of a series of FEEs spaced alonglength of a strut section of a tack device. FIG. 18 illustrates adetailed view of a cylindrically shaped FEE placed at the apex of astrut section of the tack device. FIG. 19 illustrates a perspective viewof a FEE formed as a pyramid shaped element at the apex of a strutsection. FIG. 20 illustrates a perspective view of a FEE formed as adome element at the apex of a strut section. FIG. 21 illustrates aperspective view of a FEE formed by bending the apex of a strut sectionupward. FIG. 22 illustrates a perspective view of a FEE formed bytwisting a strut section (made from wire).

IV. Method and Devices for Delivering Plaque Tacks and FormingIntravascular Constructs In Situ

A variety of delivery methodologies and devices that can be used todeploy plaque tacks, some of which are described below. For example, aplaque tack can be delivered into the blood vessel with an endovascularinsertion. The delivery devices for the different embodiments of plaquetacks can be different or the same and can have features specificallydesigned to deliver the specific tack. The plaque tack and installationprocedure may be designed in a number of ways that share a commonmethodology of utilizing an expansion force of the delivery mechanism(such as balloon expansion) and/or the expansion force of a compressibleannular band to enable the tack to be moved into position in the bloodvessel, then released, unfolded or unplied to an expanded state withinthe blood vessel.

Referring back to FIGS. 4-4D, a delivery device or catheter 11 with anouter sheath 13 is shown in a pre-delivery state. Multiple plaque tacks10 can be compressed to be loaded onto the surface of the deliverydevice 11. The outer sheath 13 can then be advanced to cover the plaquetacks 10 in preparation for delivery. In some embodiments, the plaquetacks 10 are flash frozen in their compressed state to facilitateloading onto the delivery device. The tacks can extend in an array 10 xover a given length of the delivery device.

It can be seen that the plaque tack 10 can be positioned in a patient'svasculature at a treatment site by the delivery device 11. The outersheath 13 can be withdrawn or retracted to expose and release the plaquetack 10. The tack 10 can then be expanded in any suitable way, such asby being configured to self-expand or to be balloon expanded, asdiscussed herein.

Turning now to FIGS. 23-31B, a method of delivery of one or more tack10″ will be described. As has been mentioned, an angioplasty procedureor other type of procedure can be performed in a blood vessel 7. Theangioplasty may be performed on a diseased or obstructed portion of theblood vessel 7. As shown in FIG. 23, a guidewire 40 followed by anangioplasty balloon catheter carrying balloon 42 are advanced into ablood vessel 7 in a location containing an obstruction formed by plaque.The balloon 42 is inflated at the desired location to compress theplaque and widen the vessel 7 (FIG. 24). The balloon 42 can then bedeflated and removed.

While widening the vessel 7, a dissection 44 of the plaque may be causedby the angioplasty (FIG. 25). A plaque tack or staple 10″ can then beused to secure the plaque dissection 44 to the lumen wall 7.

A delivery catheter 11′ preloaded with one or more tacks 10″ can beadvanced along the guidewire 40 to the treatment site (FIG. 26). Anouter sheath 13′ can be withdrawn, exposing a portion of the plaque tack10″. As has been discussed, the outer sheath 13′ can be withdrawn untila set point and then the position of the catheter within the vessel canbe adjusted, if necessary, to ensure precise placement of the plaquetack 10″ (FIG. 27). The set point can be for example, right beforeuncovering any of the tacks, uncovering a portion or all of a ring,uncovering a ring and an anchor, etc.

The tack 10″ can then be released in the desired location in the lumen.As discussed previously, simultaneous placement can result upon releaseof some embodiments of the plaque tack 10″. Additional plaque tacks 10″can then be placed as desired (FIG. 28). Upon placement of the secondtack 10″, an intravascular construct is formed in situ. 11. The in situplacement can be in any suitable vessel, such as in any peripheralartery. The construct need not be limited to just two tacks 10″. Infact, a plurality of at least three intravascular tacks 10″ (or any ofthe other tacks herein) can be provided in an intravascular constructformed in situ. In one embodiment each of the plurality of tacks has alength of no more than about 8 mm, e.g., about 6 mm in an uncompressedstate. In one configuration, at least one of, e.g., each of, the tacksare spaced apart from an adjacent tack by at least about 4 mm. Althoughcertain embodiments have a length of 8 mm or less, other embodiments canbe longer, e.g., up to about 15 mm long. Also, neighboring tacks 10′ bepositioned as close as 2 mm apart, particularly in vessels that are lessprone to bending or other movements. In one embodiment, each of thetacks has a relatively low radial force, e.g., having a radial expansionforce of no more than about 4 N, and in some cases about 1 N or less. Insome embodiments, tacks can be configured with as little as 0.25 Nradial force.

While a three tack construct formed in situ may be suitable for certainindications, an intravascular construct having at least 5 intravasculartacks may be advantageous for treating loose plaque, vessel flaps,dissections or other maladies that are significantly more elongated (nonfocal). For example, while most dissections are focal (e.g., axiallyshort), a series of dissections may be considered and treated as a moreelongated malady.

In some cases, even shorter axial length tack can be used to treat evenmore spaced apart locations. For example, a plurality of tacks eachhaving a length of no more than about 7 mm can be placed in a vessel totreat a tackable malady. At least some of, e.g., each of, the tacks canbe spaced apart from an adjacent tack by at least about 5 mm. In somecases, it may be preferred to provide gaps between adjacent tacks thatcan range from about 6 mm to about 10 mm.

Optionally, once the plaque tacks 10″ are in place, the angioplastyballoon can be returned to the treatment site and inflated to expand theplaque tacks 10″ to the desired state of expansion. FIG. 29 shows theplaque tacks 10″ in their final implanted state.

Referring to FIGS. 29, 30A, and 30B, it can be seen how the focalelevating elements 32 can both penetrate the plaque in the blood vesselwall and also minimize the contact area of the plaque tack 10″ with theblood vessel wall. Similarly, FIGS. 29, 31A, and 31B illustrate thepenetration of the anchors 20. It can also be seen that the position ofthe anchors 20 on the bridge 14 allow the anchors to protrudetangentially from the circular shape formed by the plaque tack 10″. Thisbeneficially allows the anchors 20 to engage the plaque or vessel wallwhile also minimizing the overall amount of contact by the plaque tack10″, similar to the focal elevating elements 32.

Use of Plaque Tack after Drug Eluting Balloon Angioplasty

The use of plaque tack devices can be combined with use of drug elutingballoon (DEB) angioplasty to manage post angioplasty dissection andavoid the need for stents. In DEB angioplasty, a drug-eluting balloon ora drug coated balloon is prepared in a conventional manner. The drug maybe one, or a combination, of biologically active agents that are usedfor various functions, such as anti-thrombotic, anti-mitotic,anti-proliferative, anti-inflammatory, stimulative of healing, or otherfunctions. The DEB is delivered on a guidewire across an area ofblockage or narrowing in the blood vessel system. The DEB is inflated toa specific pressure and for a period of time consistent with themanufactures guidelines of use for treatment purposes, as it pertainsthe drug coating and the intended outcomes, then the DEB is deflated andremoved. At this stage the medication from the DEB has been transferredto the wall of the blood vessel. Intravascular imaging by ultrasound isthen used to assess the integrity of the artery and the smoothness ofthe blood vessel surface at the site where the balloon was inflated. Thepresence of damage along the surface may be indicated as dissection,elevation of plaque, disruption of tissue, irregularity of surface. Theplaque tack is used to tack down the damaged, disrupted, dissected, orirregular blood vessel surface. This permits continuation of a“stent-free” environment even if damage to the blood vessel has occurredas a result of balloon angioplasty.

At this stage the medication from the DEB has been transferred to thewall of the blood vessel. Contrast is administered into the blood vesselunder fluoroscopic guidance or another method such as intravascularultrasound is used to assess the integrity of the artery and thesmoothness of the blood vessel surface at the site where the balloon wasinflated. In some cases, one or more of these completion studies willdemonstrate the presence of damage along the surface at the site of theballoon inflation. This damage may include dissection, elevation ofplaque, disruption of tissue, irregularity of surface.

The plaque tack delivery catheter is loaded with multiple tacks that maybe placed at the discretion of the operator, and advanced over aguidewire in the blood vessel to the location where the dissection ordisruption or irregularity has occurred. The location is specificallyand carefully identified using angiography. The plaque tack(s) is or aredeployed at the location(s) of the lesion. More than one tack may beplaced to tack down a major dissection. If more than one tack is placed,it may be placed only according to the rules of proper spacing of tacks.That is, the tack should be at least one tack axial length apart. Afterplacement of the tack, it may be further expanded into the wall of theblood vessel using a standard angioplasty balloon or a drug-eluting ordrug coated balloon (either as a stand alone (separate) device orintegral to the delivery system). The purpose of the tack is generallynot to hold the blood vessel lumen open but to tack down the non-smoothor dissected surface of the blood vessel. This “touch-up strategy”permits the resolution of the damage created by the drug-eluting or drugcoated balloon without resorting to stent placement and therebymaintaining a “stent-free” environment.

As a further measure, described above, the plaque tack device itself canbe used to deliver medication to the blood vessel. In addition to thedelivery of medication from the anchors, the tack can be coated withmedication prior to tack placement. The purpose of this activity is topermit the tack to elute biologically active agent or agents that havepositive effects on the blood vessel.

One or more of the tacks deployed in accordance with the presentinvention may be coated with or otherwise carry a drug to be eluted overtime at the deployment site. Any of a variety of therapeutically usefulagents may be used, including but not limited to, for example, agentsfor inhibiting restenosis, inhibiting platelet aggregation, orencouraging endothelialization. Some of the suitable agents may includesmooth muscle cell proliferation inhibitors such as rapamycin,angiopeptin, and monoclonal antibodies capable of blocking smooth musclecell proliferation; anti-inflammatory agents such as dexamethasone,prednisolone, corticosterone, budesonide, estrogen, sulfasalazine,acetyl salicylic acid, and mesalamine, lipoxygenase inhibitors; calciumentry blockers such as verapamil, diltiazem and nifedipine;antineoplastic/antiproliferative/anti-mitotic agents such as paclitaxel,5-fluorouracil, methotrexate, doxorubicin, daunorubicin, cyclosporine,cisplatin, vinblastine, vincristine, colchicine, epothilones,endostatin, angiostatin, Squalamine, and thymidine kinase inhibitors;L-arginine; antimicrobials such as triclosan, cephalosporins,aminoglycosides, and nitorfuirantoin; anesthetic agents such aslidocaine, bupivacaine, and ropivacaine; nitric oxide (NO) donors suchas lisidomine, molsidomine, NO-protein adducts, NO-polysaccharideadducts, polymeric or oligomeric NO adducts or chemical complexes;anti-coagulants such as D-Phe-Pro-Arg chloromethyl ketone, an RGDpeptide-containing compound, heparin, antithrombin compounds, plateletreceptor antagonists, anti-thrombin antibodies, anti-platelet receptorantibodies, enoxaparin, hirudin, Warfarin sodium, Dicumarol, aspirin,prostaglandin inhibitors, platelet inhibitors and tick antiplateletfactors; interleukins, interferons, and free radical scavengers;vascular cell growth promoters such as growth factors, growth factorreceptor antagonists, transcriptional activators, and translationalpromotors; vascular cell growth inhibitors such as growth factorinhibitors (e.g., PDGF inhibitor—Trapidil), growth factor receptorantagonists, transcriptional repressors, translational repressors,replication inhibitors, inhibitory antibodies, antibodies directedagainst growth factors, bifunctional molecules consisting of a growthfactor and a cytotoxin, bifunctional molecules consisting of an antibodyand a cytotoxin; Tyrosine kinase inhibitors, chymase inhibitors, e.g.,Tranilast, ACE inhibitors, e.g., Enalapril, MMP inhibitors, (e.g.,Ilomastat, Metastat), GP IIb/IIIa inhibitors (e.g., Integrilin,abciximab), seratonin antagonist, and 5-HT uptake inhibitors;cholesterol-lowering agents; vasodilating agents; and agents whichinterfere with endogenous vasoactive mechanisms. Polynucleotidesequences may also function as anti-restenosis agents, such as p15, p16,p18, p19, p21, p2′7, p53, p5′7, Rb, nFkB and E2F decoys, thymidinekinase (“TK”) and combinations thereof and other agents useful forinterfering with cell proliferation. The selection of an active agentcan be made taking into account the desired clinical result and thenature of a particular patient's condition and contraindications. Withor without the inclusion of a drug, any of the tacks disclosed hereincan be made from a bioabsorbable material. Various polymeric carriers,binding systems or other coatings to permit controlled release of activeagent from the tack or its coating are well known in the coronary stentarts and not reproduced herein.

In summary, the plaque tack can be used for plaque retention followingballoon angioplasty treatment of atherosclerotic occlusive disease whileavoiding problems with the use of stents due to installing a large massof foreign material in the body which may cause injury, inflammation,and/or provide sites for restenosis. In contrast with stents, the plaquetack device minimizes the material structure while only being installedat one or more plaque dissection sites that require retention. The focalelevating elements on the tack periphery minimizes the contact surfacearea of the plaque tack with the blood vessel walls and reduces the riskof causing plaque dissection or injury to the blood vessel walls. Thisapproach offers clinicians the ability to perform a minimally invasivepost-angioplasty treatment and produce a stent-like result without usinga stent.

Although this invention has been disclosed in the context of certainpreferred embodiments and examples, it will be understood by thoseskilled in the art that the present invention extends beyond thespecifically disclosed embodiments to other alternative embodimentsand/or uses of the invention and obvious modifications and equivalentsthereof. Additionally, it is contemplated that various aspects andfeatures of the invention described can be practiced separately,combined together, or substituted for one another, and that a variety ofcombination and sub-combinations of the features and aspects can be madeand still fall within the scope of the invention. Thus, it is intendedthat the scope of the present invention herein disclosed should not belimited by the particular disclosed embodiments described above, butshould be determined only by a fair reading of the claims.

What is claimed is:
 1. A catheter delivery system, comprising: acatheter shaft and a catheter sheath; a plurality of independentself-expanding tubular bodies located on the catheter shaft and spacedapart by a plurality of fixed catheter shaft protrusions, wherein eachself-expanding tubular body of the plurality of self-expanding tubularbodies is spaced apart from an adjacent self-expanding tubular body ofthe plurality of self-expanding tubular bodies by at least about 4 mm onthe catheter shaft, wherein the plurality of self-expanding tubularbodies comprises at least five self-expanding tubular bodies, eachindependent self-expanding tubular body of the plurality of independentself-expanding tubular bodies comprising: a plurality of struts; aradiopaque marker in an eyelet; and an expansion force curve thatchanges less than 1 N over a 2.5 mm outer diameter expansion range; aproximal handle with an actuator coupled to a proximal end of thecatheter sheath, wherein movement of the actuator is configured toretract the catheter sheath and uncover the plurality of independentself-expanding tubular bodies.
 2. The catheter delivery system of claim1, wherein at least a portion of each independent self-expanding tubularbody of the plurality of independent self-expanding tubular bodies has asloped orientation relative to a longitudinal axis of the independentself-expanding tubular body.
 3. The catheter delivery system of claim 1,each independent self-expanding tubular body of the plurality ofindependent self-expanding tubular bodies has an axial length and anexpanded diameter, wherein the expanded diameter is a final diameter inan unconstrained expansion.
 4. The catheter delivery system of claim 3,wherein each independent self-expanding tubular body of the plurality ofindependent self-expanding tubular bodies has an axial length toexpanded diameter ratio that is no more than about
 2. 5. The catheterdelivery system of claim 1, wherein the catheter shaft further comprisesa plurality of recesses for retaining the plurality of independentself-expanding tubular bodies.
 6. The catheter delivery system of claim1, wherein movement of the actuator is configured to retract thecatheter sheath and uncover one of the plurality of independentself-expanding tubular bodies at the discretion of an operator.
 7. Acatheter delivery system, comprising: a catheter shaft and a cathetersheath; a plurality of independent self-expanding tubular bodies locatedon the catheter shaft and spaced apart by a plurality of fixed cathetershaft protrusions, each independent self-expanding tubular body of theplurality of independent self-expanding tubular bodies comprising: aplurality of struts; a radiopaque marker; and an expansion forceconfigured to be less than 1 N if deployed in a lumen having a bore ofabout 5.0 mm; wherein each independent self-expanding tubular body ofthe plurality of independent self-expanding tubular bodies has a ratioof an axial length to an expanded diameter that is no more than about 2and at least a portion of each independent self-expanding tubular bodyof the plurality of independent self-expanding tubular bodies has asloped orientation relative to a longitudinal axis of the tubular body,wherein the axial length of each independent self-expanding tubular bodyof the plurality of self-expanding tubular bodies is no more than 15 mm,wherein the expanded diameter of each independent self-expanding tubularbody of the plurality of self-expanding tubular bodies is between 1 mmand 10 mm; a proximal handle with an actuator coupled to a proximal endof the catheter sheath, wherein movement of the actuator is configuredto retract the catheter sheath and uncover the plurality of independentself-expanding tubular bodies.
 8. The catheter delivery system of claim7, wherein the radiopaque marker comprises a flat shape with a planarouter face tangential to a cylinder extending through an outer surfaceof the independent self-expanding tubular body.
 9. The catheter deliverysystem of claim 7, wherein the radiopaque marker is in an eyelet. 10.The catheter delivery system of claim 7, wherein the expanded diameteris a final diameter in an unconstrained expansion.
 11. The catheterdelivery system of claim 7, wherein the catheter shaft further comprisesa plurality of recesses for retaining the plurality of independentself-expanding tubular bodies.
 12. A method of treating a superficial orpopliteal artery of a patient, comprising: inserting a catheter systeminto at least one of a superficial artery of a patient or a poplitealartery of a patient, wherein the catheter system comprises a pluralityof independent self-expanding tubular bodies, each independentself-expanding tubular body of the plurality of independentself-expanding tubular bodies comprising a radiopaque marker and a ratioof an axial length to an expanded diameter that is no more than about 2,and wherein the plurality of independent self-expanding tubular bodiesare located on a catheter shaft of the catheter system and are spacedapart on the catheter shaft by a plurality of fixed catheter shaftprotrusions, wherein each self-expanding tubular body of the pluralityof self-expanding tubular bodies is spaced apart from an adjacentself-expanding tubular body of the plurality of self-expanding tubularbodies by at least about 4 mm on the catheter shaft; and deployingmultiple independent self-expanding tubular bodies of the plurality ofindependent self-expanding tubular bodies from the catheter in the atleast one of the superficial artery of the patient or the poplitealartery of the patient at locations separated by regions free of metallicsupport such that the at least one of the superficial artery of thepatient or the popliteal artery of the patient is able to bend morenaturally, wherein the locations separated by regions free of metallicsupport are separated by a minimum spacing distance along the at leastone of the superficial artery or the popliteal artery.
 13. The method oftreating a superficial or popliteal artery of a patient of claim 12,wherein the radiopaque marker comprises a flat shape with a planar outerface tangential to a cylinder extending through an outer surface of theindependent self-expanding tubular body.
 14. The method of treating asuperficial or popliteal artery of a patient of claim 13, wherein theradiopaque marker is in an eyelet.
 15. The method of treating asuperficial or popliteal artery of a patient of claim 12, wherein thecatheter system comprises a handle with an actuator, an inner shaft, andan outer sheath.
 16. The method of treating a superficial or poplitealartery of a patient of claim 12, wherein the minimum spacing distance isat least an axial length of one independent self-expanding tubular bodyof the plurality of independent self-expanding tubular bodies.
 17. Themethod of treating a superficial or popliteal artery of a patient ofclaim 12, wherein at least a portion of each independent self-expandingtubular body of the plurality of independent self-expanding tubularbodies is deployed outwardly and comprises a cylindrical surface formedby a plurality of struts.
 18. The method of treating a superficial orpopliteal artery of a patient of claim 15, further comprising using theactuator to move the outer sheath proximally and uncover at least twoindependent self-expanding tubular bodies of the plurality ofindependent self-expanding tubular bodies.